Thursday, 07 February 2019 14:53

The Cross-Country Capable Cessna 310

A 310 owner reveals what ownership of a twin Cessna is really like.

The Cessna 310 was the first twin-engine aircraft produced by Cessna after World War II. The 310 prototype, powered by 240 hp Continental O-470-B engines, first flew Jan. 3, 1953. The aircraft was certified March 22, 1954. Production began immediately and continued through 1980. 

A September 1954 Flying cover story introduced the 310 to the masses with the headline, “Business Asked for It,” written by Cessna Aircraft Company president Dwane L. Wallace. Wallace cited the popularity of military surplus conversions as an indicator of the strong need for a purpose-built twin for the business flyer. He opined that “[when] properly used, [aircraft] are, without question, REAL BUSINESS TOOLS.” 

Cessna’s advertisements of the day claimed the 310 was “at least five years ahead in design and engineering,” and that “it looks and is smart and fast.” 

As for the size of the market for a new business-class twin? Wallace’s writing was prescient. “It may seem difficult to predict the future of the twin-engine market. I do know that the need is almost unlimited and, knowing the American way of doing business, I make the assumption that therefore the market is practically unlimited.”

Over the next three decades, his words rang true. A total of 5,449 Cessna 310s were produced from 1954 to 1980. They were not just business airplanes; they were TV stars, too. The Cessna 310 (a B model and D model) had a prominent role in the popular “Sky King” TV series (also a radio show) of the 1950s. 

Nowadays, the Cessna 310 isn’t the fastest airplane on the ramp, nor is it the most economical to own and operate. Many of the early 310s are no longer with us, and those that are still around are often “put out to pasture,” tied down in a far corner of the airport, surrounded by cracked asphalt or overgrown grass. 

However, some of these classic twins have been saved from a slow melt into the tarmac. Gale Cawley rescued his 1965 Cessna 310J from a miserable fate in the spring of 2002. 

Gale isn’t quite the 310 owner that Dwane Wallace had envisioned a half-century prior, as Gale had no desire to operate the airplane for business. Instead, he wanted a personal touring aircraft which would increase his three-hour-flight range. The 310 offered impressive speed and useful load for a low initial acquisition cost. He knew that it wouldn’t be the cheapest to keep in the air, but he believed the cross-country capabilities of the aircraft would offset the ongoing costs.

The 310 lived up to Gale’s expectations. His home base of South Haven Area Regional Airport (KLWA) in southwest Michigan provided a jumping-off point for flights around the United States. He owned the aircraft for 15 years before selling it to a friend.

Gale said he also wanted the 310 because, frankly, it was a cool airplane. He recounted listening to the old “Sky King” radio shows a half-century earlier. Young Gale would have likely been thrilled to know that after an extensive Air Force and airline career, he would acquire a Cessna 310 and fly it, Sky King-style, to his friend’s cattle ranch in rural Oregon! 

A Cessna 310I model, similar to Gale Cawley’s 310J, shows off its sleek lines and wingtip-mounted fuel tanks.
Cessna Flyer’s Scott Kinney had a chance to talk with Gale about what he learned from owning and flying the 310.

Q: What sort of shape was your 310 in when you acquired it?

It had lived, I’ll say, a bit of a rough life. It was delivered new to the U.S. Air Force in 1965. The civilian logs started in 1975. It had about 4,000 hours on the airframe when I bought it. The guy I got it from was a businessman. He’d used the 310 to scout for new franchise sites around the country. 

The airplane had been the subject of some drama in the years before I bought it. It had been held as evidence without flying for three years. There had been some sort of legal dispute over an annual inspection bill… the bill was something like a hundred thousand dollars. Once that finally got cleared up, it was on the market for another year before I bought it. 

I made the guy an offer that I thought was pretty low. He accepted, as he was happy to be done with it. I figured I’d gotten the 310 for a good price, so maybe wasn’t as diligent as I should’ve been with the pre-buy.

I wasn’t surprised that it was a project… turns out, though, it was a real fixer-upper! 

The left engine was run out. The right engine wasn’t timed out, but I didn’t have much confidence in it. Both props were high-time. As far as the avionics, they weren’t much better. The airplane had a dated panel with old radios. 

Q: Where do you begin with a project like that?

In the first year, I had both 260 hp Continental IO-470-D engines overhauled. The left engine was overhauled and installed by G&N Aircraft. Poplar Grove did the right engine. 

A pair of 260 hp Continental IO-470-D engines provide good performance.

So, why did I use two different shops? Well, I sent the 310’s left engine to G&N as it needed to be done immediately. They’d overhauled my Cessna 210’s IO-520 engine a few years prior. They used chrome cylinders on that one, and I had them do the same with the 310’s left engine. 

Not long after I’d had the left engine overhauled, I started having trouble with the chrome cylinders in the 210. 

I had the 310’s right engine overhauled several months after the left.

I did a little more research and found that the big Continentals didn’t do well with chrome cylinders. I also read more about other shops and saw that Poplar Grove was one of the best in the country. I decided to give Poplar Grove a try and had them use steel cylinders.

Both shops did good work. I had no trouble with either engine during my 15 years of ownership. 

I sent the props off to Tiffin Aire. They called me and asked me if I was sitting down. I knew that the props were high-time, but as Tiffin explained, there had been some “creative” record keeping in the past, and the serial numbers of the blades didn’t match the logs. Without proper records, the props were junk, and went into the dumpster. I bought new three-blade Hartzell props from Tiffin Aire.

Avionics followed shortly afterward. In addition to a much-needed radio update, I replaced the old Loran with a [Bendix King] KLN 89B GPS, and I put in a modern S-Tec 50 autopilot. I also had the instruments rearranged into a basic T configuration. Joliet Avionics (now J.A. Air Center) did the work. 

Many 310s have had avionics work done over the years.

I had a very thorough first annual and made sure everything was checked, including control rigging—pullies, cables and so on.

As all of this was getting done, I went to Flight Safety in Wichita, Kansas, to get some simulator training to make sure I was ready to fly the 310 when the work was complete. 

Q: That’s a lot of work! 

Yes, and it was not cheap, but it was well worth it. By the time all of that was done, I had a great “Sky King” airplane that flew very well. 

Q: How did it perform?

I could go fast, but that cost a lot of fuel. Depending on power settings, I saw fuel burns between 22 and 28 gph. 

I babied the engines and didn’t use more than 60–65 percent power for most flights. I liked a combination of 23 inches map and 2,300 rpm. The 23-squared combination “sang in sync,” and gave me a fuel flow of around 25 gph.

I consistently saw cruise speeds of between 165 and 170 ktas. 

With a usable fuel capacity of 130 gallons (100 gallons in the mains, 30 gallons in the auxiliary tanks), I had a range of about four hours with a comfortable VFR reserve. 

While the three-bladed props probably didn’t increase cruise speed by too much, they certainly helped with takeoff and climb. They also made for smooth and quiet operation. 

Normally, I flew with the right rear seat out in order to have more baggage space. The baggage door was located on the right side of the fuselage, which gave me easy access to the right rear seat area. 

Q: Did the aircraft have any other modifications?

Yes, it had MicroAero vortex generators (VGs) on the wings and the vertical stabilizer. The VGs provided exceptional stability at the slow end of the envelope. The airplane simply wouldn’t break hard or drop a wing in a stall. It would just go into a very smooth sink. 

The VGs allowed for slightly slower approach and landing speeds if you wanted. I always used the printed book speeds and felt those worked well. I felt that the VGs were a superb addition to the airplane.

Q: Any issues with useful load or center of gravity? 

My 310J was a six-seater, but it was shorter and a few hundeds pounds lighter than later models of the 310. 

The useful load was around 1,700 pounds. I didn’t usually come anywhere close to maximum gross. The majority of my flying was solo.

I took it to Oshkosh one year with all the seats filled and full tanks. That put my takeoff weight close to max gross. It was summer and hot, so the 310 climbed out a little slower, but it handled it well. 

Setting elevator trim correctly was very important. Whether taking off with just myself or six people in the airplane, a trim setting close to the “takeoff” mark worked well. The direction (up or down) from the mark depended on the load. When I flew alone, the aircraft was a little nose-heavy, but it wasn’t hard to compensate for that with a slight up trim setting. Q: Were there any operational quirks that you noticed?

A few. Preflights were mostly straightforward, but you needed to be careful when you were under the right wing. There’s a speed vane, which runs the Hobbs meter, on the bottom of the wing. It’s a little tab that sticks out. When air flows over it, it compresses and touches an electrical contact, activating the meter. It’s possible to accidentally snag [the tab] and bend the vane. I did, and that prompted me to get my mechanic to fix it. He placed small protective rails on each side of the vane, so it would still get airflow but wouldn’t catch on loose clothing if you brushed against it.

Fuel management was a little different, too. I learned not to fuel the main (wingtip) tanks all the way to the filler caps. If you did, fuel would siphon out the vents as your speed increased on the takeoff roll. 

The auxiliary tanks had their own peculiar features. If you select the auxiliary tanks, the engine-driven fuel pump draws from these tanks. However, the pump draws more fuel than the engines burn. The excess is pumped back into the main tanks (not, as you might assume, into the auxiliary tanks). So, even though you were burning, say, 13 to 14 gph with each engine, you could draw down the two 15-gallon auxiliary tanks in about 45 minutes. The main tank quantities would increase slightly. 

There’s another thing about the auxiliary tanks which could cause an “uh-oh” moment if you weren’t expecting it. When the airplane was cruising and hit slight turbulence, it had a tendency to yaw. When the auxiliary tanks were low, the yaw would push fuel away from the fuel intake, and the engines would sputter. The answer to this phenomenon was to either ride a rudder to stabilize the swaying or to switch back to the mains when turbulence was expected.

Another surprise was that the Janitrol cabin heater would not work unless the proper air vents to the cabin were opened. I learned this one the hard way, and had a very chilly flight!

Q: Did you operate your engines rich or lean of peak?

I only had single-cylinder EGT gauges on each engine. I ran the engines rich of peak. I figured burning just a tad more fuel was, in the long run, less expensive. I didn’t like the idea of replacing valves or cylinders if I ran them too hot. 

Q: Speaking of replacing things, how were your maintenance costs?

I had most of my work done at a Cessna-certified shop—Michigan Aviation in Pontiac, Michigan. My basic annual inspection ran about $3,600 on average. Any extra work cost more, of course. I really tried to keep up on the maintenance. I feel that good maintenance is cheap life insurance. I live in an area where hangars and other fixed costs are low, and that allowed me to spend money on quality work.

There were a few surprises during the 15 years I owned the aircraft. On this particular model of Cessna 310, the rear wing spars are vulnerable to corrosion from exhaust gases. I learned about this firsthand as I had to replace the left rear wing spar. That was a $10,000 bill. I had the work done at TAS Aviation in Defiance, Ohio. They specialize in twin Cessnas and 310s.

Q: Any other thoughts on the 310?

It was a wonderful cross-country airplane. It took me so many places: to visit my son in Connecticut, my friends in Arizona, my daughters in South Carolina and my siblings in Kansas City. I used it exclusively as a personal aircraft. I put around 400 hours on it during my ownership.

It was also not as expensive as you might think. I found the overall cost to run the 310 was about 40 percent more than my Cessna 210. 

A friend of mine talked me into selling him the 310 last year. He’s put over a hundred hours on it in the last eight months. He’s taken it around the country as well as to the Caribbean and Mexico. In retrospect, it may have been my loss and his gain!

Gale Cawley earned his private pilot certificate in 1960 at Stockert Flying Service in South Bend, Indiana. Since then, he’s flown for the U.S. Air Force, the Indiana Air National Guard and spent 33 years with American Airlines. He holds ATP, flight engineer and CFII certificates and has logged over 26,000 hours. In addition to the Cessna 310 and 210, Gale owned a farm airstrip of his own for 14 years. Scott Kinney is a self-described aviation geek (#avgeek), private pilot and instructor (CFI-Sport, AGI). He is associate editor for Cessna Flyer. Scott and his partner Julia are based in Eugene, Oregon. They are often found buzzing around the West in their vintage airplane. Send questions or comments to .

Resources

SERVICE PROVIDERS – CFA SUPPORTERS

Poplar Grove Airmotive
 
Micro AeroDynamics Inc.

ADDITIONAL SERVICE PROVIDERS

G&N Aircraft Inc.
 
J.A. Air Center (formerly Joliet Avionics)
 
Michigan Aviation
 
TAS Aviation Inc.
 
Tiffin Aire Inc.

SIMULATOR TRAINING

FlightSafety International

FURTHER READING

Jennifer Dellenbusch, “310 Tale,” 
Cessna Flyer, August 2012. 
 
Dwane Wallace, “Business asked for it: The story of the new Cessna 310,” 
Flying, September 1954.
Cessna introduced the 175 hp, four-seat Cessna 175 in 1958; with the goal of filling the gap between the 172’s price and the 182’s performance. The 175 garnered positive initial reviews. Yet only six years later, the model was discontinued. So, what went wrong? 

Just over 60 years ago, on March 22, 1958, Cessna offered its first Cessna 175 for sale. Then, as now, marketing departments used flowery language to sell the dream of “the family airplane.” 

A big and beautiful two-page ad in the April 1958 issue of Flying offered readers the “big, beautiful” new “Power-Geared” Cessna 175. The 175 promised “big-airplane stability, big-airplane comfort, big-airplane speeds”—but for a small-airplane price.

On the surface, the 175 seemed to fit perfectly in the Cessna lineup. 

At the time the 175 debuted, the 172 was Cessna’s entry-level model (the two-seat 150 wasn’t introduced until late 1958). The 182, though quite capable and roomy, was a significant step up from the 172 in both price and performance.

In 1958, a 172 cost $8,995. A standard 182 was $14,350. The deluxe 182 Skylane was $16,850. The 175, priced at only $10,995 while offering “big-airplane” features, seemed to be what General Aviation buyers desired. Flying reviewed the 175 in July 1958 and deemed it to be “an answer to a market requirement—a constructive answer.”

However, after only a few short years, the market soured on the Cessna 175. The last aircraft carrying the 175 name were produced in 1962. 

A close relative of the 172

At a distance, it’s difficult to distinguish a Cessna 175 from a Cessna 172 of the same era. This is especially true for earlier 175 models, before the 175A adopted a noticeably “humped” cowl. The 175 and 172 airframes were developed concurrently, with extensive parts commonality. 

Delays with the Cessna 175’s newly-developed Continental GO-300A powerplant meant that the 175 debuted two years later than the Cessna 172 and 182, which were both first sold in 1956. 

The 175 prototype took to the skies over Wichita April 26, 1956. The Cessna 175 received type certification on January 14, 1958. An aggressive schedule brought the aircraft to market by late March 1958. 

 

Model evolution

The 175 and 172, though extremely similar when viewed from across the tarmac, do exhibit differences, especially under the cowl and in the cabin. 

Early straight-tail 175s and 172s (pre-A models) have the same fuselage dimensions. However, the firewall position and firewall structures differ. 

The 175’s firewall is a stepped design, rather than the flat firewall of the early 172. The 175’s firewall is further rearward on the fuselage than that of the 172, allowing for a longer, more gradually-tapered cowl with larger inlets for cooling air. The cowls of early 175s appear more like those found on Cessna 182s.

The position of the 175’s firewall affects the position of other internal fuselage components. The instrument panel is correspondingly further rearward, in a wider area of the fuselage. Cessna engineers took advantage of this increased panel width and designed a new instrument panel exclusive to the 175; the early 172’s “shotgun panel” layout was not used. 

The 175’s instruments are clustered on the left side of the cabin, in clear view of the pilot. Though not a quite a linear six-pack arrangement, the 175 has a modern-looking instrument panel. The instrument panel layout was “easy-to-work, easy-to-read,” according to Cessna’s marketing. 

In 1960, the Cessna 175A—as well as the 172A—received Cessna’s new swept-tail design, paired with the “fastback” fuselage. The 175A and later models are fitted with a distinctive “humped” cowl. 

The 172B borrowed from the 175’s design: Cessna adopted the stepped firewall of the 175, a longer engine mount and cowl, and also changed the instrument panel layout to match the 175’s. 

The 172B and 175B fuselages—and in fact, the entire airplanes—are dimensionally nearly identical.

The 175’s wing structure is very similar to that of the 172, with differences in the internal inboard third of the wing to account for the fuel tanks. 

 

Fuel

The 175 has two tanks, one in each wing, that hold a total of 52 gallons of fuel; an upgrade from the 42 gallons of the 172.

Due to the location of the fuel pickups in the tanks, only 42 of the 52 gallons is usable in all flight conditions. The 175’s POH states that an additional nine gallons are usable in “level flight.” However, the 175’s TCDS carries a rather ominous warning: “The Models 175A and 175B fuel system does not comply with CAR 3.433 and 3.434 for horsepower greater than 167 at the best angle of climb which is the most critical attitude.”

 

Options

The deluxe trim model offered from late 1959 onward was called the “Skylark”—all Skylarks are 175s, but not all 175s are Skylarks. Some were fitted with Levelair T-2 or Tactair T-3 autopilots. 

The 175 could be ordered as a seaplane, also. This option boosted gross weight by 100 pounds for the 175A and 175B.

In addition, an 18-gallon auxiliary tank was available for the 175 as a factory-installed option. The tank was installed on the baggage compartment floor with a filler neck on the right side of the fuselage. An electric pump connected the tank to the right wing tank.

Powerplant

As the 175 was being developed, Continental Motors offered Cessna the exclusive use of a new high-rpm 175 hp variant of the O-300. This new powerplant, which would become the Continental GO-300, promised increased performance with a negligible weight penalty. 

According to a July 1958 Flying review of the 175, Cessna engineers debated whether the high-rpm engine design would be better served by connecting a smaller-diameter propeller directly to the crankshaft or by gearing down to a larger prop. Connecting the propeller directly to the crankshaft in a standard arrangement would be no doubt simpler mechanically, but the geared reduction drive offered the lure of more efficient operation, especially at takeoff and climb speeds. They chose to use a geared drive. 

Cessna Flyer contributing editor and A&P/IA Steve Ells explains how it works:

“The reduction gear assembly consisted of spur-type gears with the propeller shaft located above the engine crankshaft centerline. The propeller’s center was approximately nine inches above the center of the crankshaft. This arrangement enabled the installation of a much longer propeller than was possible in any direct-drive engine. The Cessna 175 landplane swung an 84-inch McCauley prop that produced more thrust than the 172’s 76-inch propeller. 

The offset of the reduction drive still provided the required flat nose tire and flat strut prop-to-ground clearance distance mandated by airplane certification regulations. An enormous 90-inch prop was approved on the 175A and 175B when on floats.

A propeller-to-engine reduction ratio of 0.75 provided 2,400 prop rpm at the takeoff power setting of 3,200 crankshaft rpm. At the recommended cruise rpm of 3,000 on the tachometer, the prop settled down to 2,250 rpm. This slower prop speed resulted in lower prop-generated noise at both takeoff and cruise power settings.”

The 175 hp GO-300A spun at a maximum of 3,200 rpm; noticeably faster than the non-geared O-300 which redlined at 2,700 rpm. The difference in engine rotational speed had a price. While the O-300 had a TBO of 1,800 hours, the GO-300s found in 175s had a TBO of 1,200 hours. 

The GO-300A of the early 175 was replaced by the GO-300C and -300D in 1959. The last 175s used the GO-300E and swung a constant-speed propeller. 

The decision to use the high-rpm GO-300 engine and geared reduction drive would ultimately determine the success of the 175 and Skylark names. 

Performance

The most noticeable difference between the 175 and 172, aside from the engine, reduction drive and panel layout, is their relative performance. 

Steve Ells found this to be the case several decades ago: 

“In 1985, I was dropped off with a box of tools at an unimproved strip across from Kenai, Alaska, on the west side of the Cook Inlet to troubleshoot engine problems in a customer’s Cessna 175. I loosened up a draggy exhaust valve with a liberal dosing of Kroil penetrating oil before flying back. 

Although the inlet is less than 30 nm across at that point, I knew if I had to ditch in the cold waters I was a goner, so I climbed up to 8,500 feet before turning toward home and the other shore. 

The GO-300 never missed a lick and I was very impressed with how much more power it seemed to have versus the 172s I have flown previously.” 

Pilots with time in unmodified straight-tail 172s know that they’re sweet-handling aircraft; they also realize that the 145 hp Continental O-300 gives merely adequate performance. Cruise speeds are typically around 120 mph tas (104 ktas). Though early 172s are light airframes (over 300 pounds lighter than today’s 172s), their low MTOW of 2,200 pounds limits payload. After filling the tanks, about 640 pounds are left for passengers and luggage. 

A stock 175 weighs about 100 pounds more than its 172 counterpart, but that is offset by a 150-pound increase in MTOW from 2,200 to 2,350 pounds. Useful load is best on the standard model (just over 1,000 pounds) and lower on the deluxe Skylark, at approximately 950 pounds. After the tanks are filled, the 175 Skylark has a slightly lower payload than the 172; in the 630-pound range. 

Cessna claims the 175 cruises in the 135–140 mph tas range (117–122 ktas), and with larger tanks than the 172, the 175 can go about 100 miles further nonstop. 

According to book numbers, the 175 also sports much-improved short-field and climb performance, nearly on par with the 182. The 175 Owner’s Manual states the aircraft can climb at 850 fpm at sea level at its full 2,350-pound mtow, while the takeoff ground roll consumes only 735 feet of runway. At lighter weights, climb rate approaches 1,400 fpm, and the 175 needs just 345 feet to get off the ground. 

 

Engine issues

The 175, at least on the surface, offered a great value proposition for buyers. The 1958 and 1959 models of the Cessna 175 sold well: 1,239 left the factory in the first two years of production.

Cessna’s 1959 ads claimed that the 175 could provide “8 cents-per-mile operation,” including fuel, maintenance, storage, insurance and depreciation. 

However, issues with the GO-300 engine soon challenged Cessna’s assertion. Many GO-300s never made it to the promised 1,000-hour TBO, and those that did often required cylinder work to get there.

Steve Ells shares his thoughts on the engine: 

“It’s often thought that the 175 lost favor with buyers because the engine was rumored to be unreliable. The GO-300 initially had a 1,000-hour TBO (amended to 1,200 in 1968), which was not uncommon for that era. One very experienced engine builder described the GO-300 to me as a powerful smooth-running engine, but cylinder problems seemed to head the list of issues. 

One plausible theory is that pilots that had been flying Cessna single-engine airplanes at cruise rpm of 2,350 to 2,500 were very reluctant to cruise at the GO-300’s preferred 3,000 rpm, so they pulled the throttle back to what they thought was the “correct” rpm. 

I believe that if the tachometer had shown propeller rpm instead of crankshaft engine rpm, the engine reputation would not have suffered as much as it did.”

The lower power settings may have “sounded” right to pilots used to standard engines, but at low rpm, the GO-300 didn’t develop sufficient oil pressure to provide lubrication and cooling. 

A 1972 Flying article entitled “Cessna’s Neglected 175” concurred: “People ran the 175s as they would have a 172… the engines warped their valves, broke rings, scored cylinders, cracked pistons. The bad-mouthing began as engines started to fold in 500 hours of a promised 1,000 [hour] TBO.”

Airflow for cooling also likely suffered at low speeds in early tightly-cowled 175s, contributing to premature cylinder issues. Later 175s suffered the opposite problem. The redesigned cowl of the A and later models brought plenty of air to the cylinders. Shock cooling became an issue in low- or idle-power descents.

The Cessna 175’s POH listed cruise speeds and fuel burns down to 36 percent power and 2,400 engine rpm, which may have exacerbated these issues by giving pilots the impression that this was a “safe” power setting.

In addition to the engine problems, the GO-300’s gearbox was prone to issues if operated incorrectly. Numerous posts on today’s Cessna 175 type forums warn pilots to always keep a load on the engine; and under no circumstances to let the propeller “drive” the engine at idle. Gradual, constant-power descents are advised.

 

Declining production

By 1960 and the 175A model, sales had slowed: 540 175As were produced in 1960. Only 225 175B aircraft were sold in 1961.

The 1962 175C model, sporting a Continental GO-300E driving a constant-speed propeller, offered performance and payload improvements. Despite better climb numbers and a greater MTOW of 2,450 pounds, the 175C didn’t sell any better. Only 117 175Cs were produced.

When a 175 isn’t a 175 any longer

In 1963, with a marketing sleight-of-hand, the model that would have been the Cessna 175D morphed into the “Powermatic P172D Skyhawk.” Ostensibly, Cessna calculated that the 172 brand was stronger and the change would help dissociate the airframe from the troubled 175/Skylark name. 

Cessna upped the MTOW to 2,500 pounds, which gave the P172D an impressive 1,100 pounds of useful load. The P172D dropped the fastback fuselage and received the “OmniVision” rear window. It also was fitted with cowl flaps for better engine cooling. 

However, the market didn’t bend. Only 72 of the Powermatics were built; 69 in the United States and three which were assembled under license by Reims Aviation in France as FP172Ds. (The “F” prefix was for “French-produced.”) 

The 175 lives on

Cessna 175 and P172D  production ceased in 1963, after a total production run of 2,118 aircraft. The Skylark was abandoned—almost. 

In addition to the three FP172Ds which had been delivered to European buyers by Reims Aviation, a fourth airframe had been shipped to France.

In mid-1963, Reims engineers converted this airframe into a prototype military liaison aircraft. It featured a 210 hp Continental IO-360-D powerplant matched with a constant-speed propeller.

This proof-of-concept would inspire a number of variants—several of which Cessna eventually certified under the 175 Type Certificate, including the US Air Force T-41B through D (and non-USAF versions, the R172E through J) and the R172K Hawk XP (profiled in the April 2018 issue of Cessna Flyer). 

Cessna produced 2,080 of these IO-360-powered “172s” which were, at least from a certification basis standpoint, 175s.

Though the Reims Rocket is nearly equivalent to the T-41B and shares a common ancestry, it is not included on the 175’s Type Certificate, nor was the French-produced FR172K Hawk XP.

In late 1978, Cessna created a version of the airframe with a retractable undercarriage, a 180 hp Lycoming O-360-F1A6 engine and a three-bladed constant-speed prop. This aircraft, the 172RG Cutlass RG, though a 172 in name, is also on the 175 Type Certificate. 1,191 172RGs were produced between 1980 and 1985.

In total, some 3,271 of these “175 derivatives” left the Cessna factory.

The early positive reception for the 175, the later success of “souped-up 172s” like the R172K Hawk XP, and the number of STC’d 180 hp conversions of legacy 172 airframes demonstrated that there was, and still is, a market for an airplane that is a step up from a standard 172. 

However, the Cessna 175’s reliance on a new, unproven engine to achieve “big-airplane performance” was its ultimate undoing.

As a further testament to the “172-plus” concept and the 175 airframe itself, many of today’s still-flying 175s have been upgraded with one of several STC’d engine conversions. 

Next month: Cessna 175 STCs and modifications, and a flight test of an O-360-powered Skylark.

 

Scott Kinney is a self-described aviation geek (#avgeek), private pilot and instructor (CFI-Sport, AGI). He is associate editor for Cessna Flyer. Scott and his partner Julia are based in Eugene, Oregon. They are often found buzzing around the West in their vintage airplane. Send questions or comments to .

SOURCES (ONLINE)
Type Certificate Data Sheet No. 3A17 Rev. 46, May 14, 2007; Skylark Associ-ation International Forums, cessna175.org; Flying, Apr. 1958, Jul. 1958, Sep. 1958, Mar. 1959, Jun. 1959, Nov. 1961, Aug. 1972, Sep. 2008. [Note: many back issues of Flying, including all cited here, are available free on Google Books: books.google.com.]
 
SOURCES (PRINT)
“Airlife’s General Aviation: A Guide to Postwar General Aviation Manufacturers and Their Aircraft” 
R.W. Simpson. Shrewsbury (UK): Airlife Publishing, 2000. 
 
“Cessna 172: A Pocket History”
Ron Smith. Stroud (UK): Amberley, 2010. 
 
“Cessna: Wings for the World”
William D. Thompson. Bend, Oregon: Maverick Publications, 1991.
 
“The General Aviation Handbook”
Rod Simpson. Hinckley, Minnesota: Midland, 2005. 
 
Jane’s All the World’s Aircraft 
New York, NY: McGraw-Hill, 1967. 
 
“The Planes of Wichita: The People and the Aircraft of the Air Capital”
Daryl Murphy. Bloomington, Indiana: iUniverse, 2008. 
 
“T-41 Mescalero: The Military Cessna 172” Walt Shiel, Jan Forsgren and Michael R. Little. Lake Linden, Michigan: Slipdown Mountain Publications, 2006.
 
Resources
FURTHER READING
“Cessna’s In-between Single: The R172K Hawk XP” 
by Steve Ells. Cessna Flyer, April 2018.

Available at https://www.cessnaflyer.org/magazines/item/1036-april-2018-cessna-flyer-magazine.html

$75 million plan will modernize infrastructure

 

MOBILE, ALA. – Continental Motors Group Ltd. (CMG), an AVIC International Holding (HK) LTD company (HKEX: 232.HK), announced that the foundation work for its new manufacturing facility has started.

Blue Marlin is the code name for a significant investment program that focuses on the future of Continental Motors Group.

It is a multifaceted project that includes building a greenfield manufacturing and office building in Mobile, Alabama—where CMG has based its operations for over 50 years, thus renewing its commitment to the local community and employees.

The new facility will be nearly 275,000 square feet, with the majority being dedicated to advanced engine and parts manufacturing for all Continental Motors Group product lines. It will be populated with brand-new manufacturing equipment and include a special area designated for evaluation of new manufacturing techniques and processes, including additive manufacturing and automation.

Building a new factory is only one part of the $75 million plan to profoundly transform Continental Motors and the way the company designs, manufactures, certifies and supports products.

Modernizing its infrastructure and enhancing its customer and technical support service capabilities around the world allows the CMG teams to provide 24/7 support and assistance in the near future.

A groundbreaking ceremony was held Aug. 22, 2018. Speakers at the event included Rhett Ross, President and CEO of Continental Motors Group. Representatives from the Mobile Area Chamber of Commerce, Alabama Department of Commerce, Mobile County Commissioner, Mobile Airport Authority and other organizations were also present.

The factory is set to be completed and in operation in 2020. The construction site is being observed by a time-lapse camera.

Follow the progress of Blue Marlin’s construction at continentalmotors.aero

More information about Continental Motors can be found at continentalmotors.aero

Thursday, 14 June 2018 12:56

Engine Overhauls, Illustrated

Most engines are “sent out” to specialty shops for overhaul. Peek behind the doors at Triad Aviation as author Jacqueline Shipe guides you through engine overhaul procedures. 

The single biggest repair expense most airplane owners will ever face is an engine overhaul. Overhaul costs increase every year along with parts prices. The engine overhaul process has become somewhat of a specialized procedure. Most mechanics won’t consider overhauling an engine themselves. The engine is typically removed and sent out for overhaul.  

 

When is an overhaul necessary?

The first step in the overhaul process is determining that an engine does in fact need an overhaul. Mere time since the last overhaul doesn’t always equate to needing to overhaul an engine. Part 135 operators must legally comply with engine manufacturers’ recommended times between overhauls. However, the only legal requirement for everyone else is engine condition. 

An engine that is run regularly (at least once a week) with cylinders that have good compressions with no exhaust valve leakage is a good candidate to keep running. Regular oil changes must consistently demonstrate that no excessive metal is being produced by the engine. Such an engine can safely and legally go beyond the manufacturer’s recommended time between overhauls (TBO). 

Cylinder issues can be resolved by replacing the affected cylinder, or by completing a “top” overhaul and replacing all the cylinders.

So, what might indicate it’s time for an overhaul? Excessive amounts of metal that have been determined to be coming from the bottom end parts (camshaft, lifter bodies, gears or crankshaft bearings) is one sign. If an engine has crankcase cracks that are outside allowable limits, it’s time. If an engine has problems producing its rated power even though cylinder compressions are good and fuel and ignition systems are within limits and working properly, an overhaul is likely needed in the near future. (For more, see “Is Your Engine Worn Out?” by Steve Ells in the October 2017 issue. —Ed.)

 

The overhaul process

An overhaul always includes a complete disassembly of the engine, thorough cleaning and inspection of parts, repair of parts as needed and disposal of defective parts. 

Major items such as the crankshaft, crankcase and connecting rods are subject to special inspections. 

Parts that are subjects of Airworthiness Directives or Service Bulletins are typically replaced or repaired in accordance with the steps outlined in the AD or bulletin. 

Parts are measured for excessive wear and proper clearances. The allowable dimensions and clearances are given in the manufacturer’s overhaul manual in two separate columns; one for manufacture (new) limits and one for service limits. The service limits are larger and allow for looser fits than manufacture limits. Some shops rebuild engines based on manufacture limits, while others use service limits. 

 

Crankshaft

The crankshaft is arguably the most important component in an aircraft engine. It absorbs the force generated by the reciprocating strokes of the pistons and rods and transforms it into rotational force for the propeller. The crankshaft is continuously subjected to loads and stresses from engine operation and the rotating propeller. Cracks or defects on a crankshaft can cause sudden engine failure or excessive, premature wear on the bearings. As a result, the crankshaft is probably the most inspected, measured and scrutinized part in the entire engine during the overhaul.

After engine disassembly, the crankshaft is cleaned and degreased in a chemical vat, dried and inspected. Most shops have a Magnaflux machine to inspect the crankshaft for cracks. 

The crankshaft is clamped between two copper-plated pads and an electric current is sent through the crankshaft to magnetize it. 

The crankshaft is then coated with a fluorescent solution containing magnetic particles. If there is a fracture in the crankshaft, the magnetic particles will align along the edges of the fracture. The fluorescent solution makes cracks easy to see under a black light. 

Once the magnetic particle inspection is complete, the crankshaft is cleaned again, and each journal is polished. Some shops have a machine that spins the crankshaft while a polishing rag is held stationary on one journal at a time with a special tool. Other shops use a machine with a circular cloth that is spun around each journal. The polishing process removes light scoring and surface corrosion as well as providing a clean journal surface so that good measurements can be obtained of each journal. 

Excessive scoring or pits caused by corrosion that cannot be removed by polishing the crankshaft can usually be removed by grinding off a specified amount of material. The manufacturer sets the sizes to which the crank can be reground, and it varies based on the engine model. Most Lycoming crankshafts can be ground to three-thousandths, six-thousandths or ten-thousandths of an inch undersize. Continental usually allows five-thousandths or ten-thousandths undersize. 

Once the crankshaft has been ground down to limits (referred to in the field as “ten under”), any further scoring or pitting defects in the journals will most likely result in the crankshaft being scrapped at the next overhaul. Reground crankshafts require oversize bearings to maintain proper clearances.

When all the machining and polishing processes are complete, the diameters of the main bearing journals and connecting rod bearing journals are measured with a micrometer at several points around the circumference of each journal. The smallest measured diameter is used to determine if each journal is within limits. 

The inside diameters of the connecting rod and crankcase main bearings are measured by installing the bearings and temporarily installing the bolts and nuts, securing the case halves and connecting rod halves together. A telescoping gauge is then used to measure the inside diameter of the bearings. Clearances are obtained by subtracting the journal diameter from the bearing internal diameter. Clearances must fall within the limits set by the manufacturer.

The crankshaft is also measured for straightness (or run-out) using a dial indicator. The crankshaft is placed in a holder that supports the crankshaft while still allowing it to rotate. A dial indicator reading is then usually taken on the rear main journal as well as the crankshaft flange. The readings must not exceed allowable limits. 

It is a fairly rare occurrence when a crankshaft is rejected. Aircraft crankshafts are constructed with high-quality metals at manufacture and, barring misuse or a prop strike, generally pass inspections through multiple overhauls. 

If the crankshaft needs to be replaced for any reason, it adds a significant amount to the cost of an overhaul. Some shops try to help owners by finding a serviceable used crankshaft, which is usually one-half to one-third the cost of a new crankshaft. 

 

Crankcase

The crankcase provides the housing to hold all the internal components (crankshaft, camshaft, rods) as well as providing a place to attach the cylinders, accessory case and oil sump. The crankcase is made of cast aluminum and must be strong enough to absorb all the opposing forces of the engine as it is in operation. 

Crankcases receive a thorough cleaning and inspection at overhaul. 

Some shops use abrasive media to clean the case and some use a chemical vat. Chemical-only cleaning processes are preferred because residue from blast material is difficult to remove from all the creases and recesses in the case. Any leftover media causes scratching and scoring once the engine is placed back in operation. 

Crankcases are inspected for cracks using a dye penetrant inspection. The case is saturated in fluorescent colored penetrant, then rinsed. The penetrant seeps into cracks making them easily seen once the case is sprayed with developer or examined under a black light.

Some cases are more prone to cracking than others. As an example, Lycoming “narrow deck” cases crack far more often than the thicker “wide deck” cases. Narrow deck cases utilize cylinders that have a thinner hold-down flange. The cylinder base nuts are Allen head (internal wrenching) types; while the wide deck cases have cylinders with thicker hold-down flange with standard six-sided nuts. Cracks can sometimes be welded and repaired depending on their location. 

Cases can have fretting damage or small areas of corrosion where the case halves are joined, especially near through-bolts. Cases with damage are generally sent to specialized machine shops such as DivCo or Crankcase Services to have the mating surfaces machined smooth. Some shops “line bore” the center bearing areas so that the crankshaft main bearings are perfectly straight and aligned with the each other. 

Regardless of whether the case is simply cleaned and inspected or sent out for further machine work, the mating surfaces of the case halves must be smooth and perfectly flat to ensure a proper seal once they are assembled. A silk thread is used to seal the case halves along with a special non-hardening compound designed to hold the thread in place as the case halves are assembled. Any irregularities in the mating surfaces will result in case leaks. 

Crankcases, like crankshafts, are expensive to replace and can add significantly to the cost of an overhaul if replacement is required. 

 

Connecting rods

Connecting rods are Magnafluxed, cleaned and dimensionally checked at overhaul. Connecting rod bearings along with the bolts and nuts that secure the rod halves are always replaced at overhaul. Connecting rod bushings are not always replaced, depending on the wear and condition on the bushings. 

The rods are checked with special dowel tools to be sure they aren’t bent or twisted. The connecting rod is turned sideways and held in a vertical plane. One dowel slides through the connecting rod bushing and the other through the crankshaft bearing. After they are inserted, the ends of the dowels are laid on perfectly-matched metal blocks. The four ends of each dowel pin should lay perfectly flat if the rod is not twisted at all. 

The dowels are left in place and a special gauge is attached to the end of the crankshaft bearing dowel. This gauge telescopes and it is extended until it touches the end of the shorter connecting rod bushing dowel.

After this measurement is made, the gauge is removed and placed on the opposite end of the crankshaft bearing dowel. If the rod is square and not bent, the gauge will line up and touch the short dowel on the opposite side without being extended or shortened.

 

Camshaft and lifters

The camshaft and lifter bodies are generally replaced or sent out to be reground to remove any light scoring marks or surface deformities. The camshaft lobes go through a carburizing process to harden them at manufacture. The depth of the carburized layer of metal is not very deep (about fifteen-thousandths of an inch) and it is possible for machine shops to accidentally grind below that layer. The camshaft lobe would wear down rapidly once placed in use if that happened. Additionally, the lobes are not only elliptically shaped, but they have a slight taper across the top of the lobe to ensure that the lifter body spins as it contacts the lobe. It takes very precise machine work when grinding the lobe to maintain its original shape and the taper across the top. Camshafts should only be sent to high-quality, experienced machine shops like Aircraft Specialties for machining work. 

Camshafts are not terribly expensive when purchased new (compared to major parts like crankshafts or cases). Typically, the cost of buying a new camshaft and all the lifters is only a few hundred dollars more than having the old ones reground. 

(For more on camshafts and lifters, see Jacqueline Shipe’s July 2017 article in Cessna Flyer. —Ed.)

Accessory case, oil sump, gears

The accessory case and oil sump are typically cleaned, inspected and reused. The Lycoming oil sumps that have intake pipes routed through the sump are reswedged around the intake pipe end to ensure there are no leaks down the road. This involves using a special tool which swells the pipe back out a little so that it forms a better seal when it is inserted into the sump opening.

The accessory case is inspected with dye penetrant and cleaned. The gears in the accessory case are cleaned, Magnafluxed and reused. 

 

Cylinders

Individual cylinder assemblies can be overhauled, but by the time the valves, guides and seats are replaced, the cost is almost equal to the cost of a new cylinder. Most overhaul facilities that I’m familiar with install new cylinders rather than overhauling the old ones. 

The cylinder must absorb the heat and pressure of combustion every time it completes a cycle while in operation. Metal fatigues over time and with a relatively low cost difference between new and overhauled cylinders, new cylinders are the best choice for long-lasting operation. They also typically come with their own warranties, so shops like them. 

It’s important to note that there is no logbook tracking for individual cylinder assemblies. Times in operation are kept of engines, but not of the individual engine parts. Therefore, it is impossible to really know how much operating time cylinders have on them when purchasing overhauled cylinders outright. The times that are on the existing installed cylinders on an engine can be difficult to trace unless they were new at the time of installation. 

 

Fuel system

The fuel injection system or carburetor is generally sent out for overhaul at a specialty shop or replaced with a new unit. Very few overhaul facilities overhaul the fuel system components in-house. Even Lycoming gets all the fuel injection system components and carburetors for both their new and rebuilt engines from Avstar Fuel Systems in Florida. 

 

Accessories and other items

All other accessories are typically sent to specialty shops for an overhaul or are replaced with new. Magnetos, ignition harnesses and vacuum pumps are generally replaced with new units. Alternators and starters are generally rebuilt. 

Oil coolers should always be sent out for specialized porting and cleaning to be sure all metal particles and sludge buildup is completely removed. The oil passages through the coolers make several 180-degree turns. Small metal particles and contaminants build up in the coolers around the curves and it is impossible to remove all the debris with just a simple flushing. Oftentimes, new oil coolers are fairly inexpensive, and it is easier and cheaper to simply replace them rather than overhaul them. 

All hoses should be replaced at overhaul. Hoses deteriorate with age and exposure to heat, and should be replaced periodically. New hose installations also help prevent contaminating the freshly overhauled engine with any sludge or debris remaining in the hose. 

It’s also a good idea to replace all the SCAT hoses. Most of the tubing (like the aluminum oil return lines) is cleaned, inspected and reused.

 

Choosing an overhaul facility

Engine overhauls are extremely expensive. When it’s time to overhaul an engine, choosing a high-quality facility to do the job is important. The best way to choose where to send an engine is usually by personal referral. Ask other owners what shop(s) they have used and what the long-term results have been. Owners or operators that have put three to five hundred hours on an engine usually know by that time whether the overhaul was a good one. Low cylinder compressions, oil leaks or other problems are signs that the overhaul may not have been the best. 

Most Part 91 owners only have to face an engine overhaul once. The process can be stressful to go through. Owners who do lots of research ahead of time, understand the process and ask lots of questions can help to avoid major problems down the road. 

 

 

 

Jacqueline Shipe grew up in an aviation home; her dad was a flight instructor. She soloed at age 16 and went on to get her CFII and ATP certificate. Shipe also attended Kentucky Tech and obtained an airframe and powerplant license. She has worked as a mechanic for the airlines and on a variety of General Aviation planes. She’s also logged over 5,000 hours of flight instruction time. Send question or comments to

 

Resources

ENGINE OVERHAULS Airmark Overhaul airmarkoverhaul.com

Granite Air Center graniteair.com

 

Poplar Grove Airmotive poplargroveairmotive.com/engine-shop

RAM Aircraft ramaircraft.com

Triad Aviation hhtriad.com

 

CRANKCASE INSPECTION / REPAIR Aircraft Specialties Services aircraft-specialties.com

Crankcase Services, Inc. crankcaseservices.com

DivCo, Inc. divcoinc.com

 

FUEL SYSTEM OVERHAUL Avstar Fuel Systems, Inc. avstardirect.com

 

Aircraft Accessories of Oklahoma aircraftaccessoriesofok.com