October 1, 2001
Steven W. Ells
There are really three Cessna Skyhawks — the early ones (1956 to 1967) with the 145-horsepower Continental six-cylinder engines; the 1968 through 1984 models with the 150- or 160-hp four-cylinder Lycoming engines; and the newest versions — the 1996 and newer 160- and 180-hp airplanes with fuel-injected four-cylinder Lycomings. How do they differ, and how do they measure up to their retractable-gear sibling, the Cessna 172RG Cutlass?
With Cutlass prices already bumping the ceiling of the budget-buy category, we're going to leave the more expensive 1996 and newer 172s for another day.
The Cutlass was produced from 1980 to 1985. While it's easy to assume that Cessna answered the industry need for a simple, low-cost complex trainer by grabbing a 172 fuselage off the shelf and swapping the fixed landing gear for one of the company's retractable landing gear systems, technically these two airplanes come from different branches of the Cessna tree.
The 172RG falls under the same type certificate as the Cessna 175 (a 172-like fuselage with a 175-hp Continental GO-300 engine, larger fuel tanks, and a 2,350-pound gross weight), the Hawk XP (with a 195-hp Continental IO-360 engine), and the R172 airplanes that were sold almost exclusively as military trainers under the T?41 moniker. Most T?41s also had Continental six-cylinder IO-360 powerplants, tweaked to 210 hp.
If an aviation archeologist needed evidence to support a postulate that general aviation grew up in the second half of the twentieth century, studying the 172 line would provide solid factual evidence.
The 172 evolved as Cessna responded to the flying public's desire for a more modern, comfortable, and safer airplane. As more avionics, larger fuel capacities, and better accommodations were incorporated, the airplanes got heavier, necessitating maximum gross weight increases.
When first introduced in 1956, the 172 had a maximum gross weight of 2,200 pounds. Gross weights were increased to 2,250 pounds in the 172C (1962), and bumped up another 50 pounds with the introduction of the 172D in 1963. Gross weights stabilized there at 2,300 pounds for 16 years until the introduction of the 172P in 1980, when Cessna upped the maximum gross weight to 2,400 pounds — where it stayed until the end of production in 1986.
It should be said here that in 1980 and 1981 Cessna produced a number of 172Qs. These 180-hp models, built for instruction at the mile-high runways of Embry-Riddle Aeronautical University's Prescott, Arizona, campus, had a maximum gross weight of 2,550 pounds.
The 172RG was introduced in the 1980 model year with a maximum gross weight of 2,650 pounds.
Current weight-and-balance reports for three 172s — Rich Jensen's "used but not abused" 1966 172G, Steve Brown's 1972 172L, and Jim Gibbs' 1980 172RG — provide real-world load-hauling and performance numbers. All of these IFR-certified airplanes are similarly equipped with full IFR panels and comparable radios stacks. Brown's Lycoming-powered 172 has had the factory exhaust system replaced with a Power Flow exhaust system. With this exception, none of the airplanes is loaded with gee-whiz stuff that can quickly nibble into the useful load.
Jensen's no-frills cruiser has an empty weight of 1,399 and a useful load of 901 pounds. With a full fuel load of 234 pounds, or 39 gallons, there are 667 pounds left over for people, baggage, and flying supplies.
Brown's 1972 airplane has an empty weight of 1,385 pounds, resulting in a useful load of 915 pounds. With a full fuel load of 252 pounds, or 42 gallons, there are 663 pounds of full fuel useful load.
Gibbs' Cutlass, which he bought new in 1981 and qualifies as a low-time 172RG with only 2,368 hours on the tach, has a basic empty weight of 1,701, resulting in a useful load of 849 pounds. Gibbs is well aware that, with 66 gallons of fuel capacity, his Cutlass is limited to 453 pounds of useful load when the tanks are full. Put another way, fixed-gear 172s can easily cruise for three and a half hours (with an hour's reserve) on a full load of fuel; a Cutlass has enough fuel to cruise for six hours with the same reserves.
Jensen's 172, one of the last models that was powered by the oh-so-smooth six-cylinder Continental, allows Jensen to flight plan for 105 knots with a fuel consumption rate of eight gallons per hour.
Brown, owner of the 150-hp Lycoming-powered 172L, conservatively plans for 105 knots and eight and one-half gallons per hour, but says his airplane really goes slightly faster than 110 knots.
Gibbs cites realistic cruise fuel burns of 9 to 9.5 gallons per hour, with true airspeeds of 130 to 135 knots, at a 75-percent power setting of 2,400 rpm and 24 inches of manifold pressure when leaned to 75 degrees rich of peak.
Comparison numbers indicate that there are slight performance improvements between Jensen's pre-1968 Continental-powered 172 and Brown's later, highly favored Lycoming-powered Skyhawk. The more modern instrument panel layout and the simplicity and dependability of the Lycoming four-cylinder are definite pluses. From 1975 on Cessna worked hard on reducing drag. This, combined with the 160-hp engines installed beginning in 1977, resulted in slightly better speeds.
But that new engine, the Lycoming O-320-H2AD, was a totally new design that proved not to be very reliable. It suffered serious camshaft/hydraulic lifter problems, especially when compared to the "bulletproof" O-320-E2D that it replaced. Five airworthiness directives (ADs) were issued in rapid succession against the engine. Compounding the problem was the introduction of the first "dual" magneto, the Bendix D-2000 series, on the same engine; it also generated a flurry of ADs. This dual mag had two separate magnetos in a single housing, rotated by one drive gear. The single drive gear seemed to contradict the aviation industry's traditional and historical dependence on redundancy as the primary guarantor of safety. The result was soft prices for these airplanes, and a bruise in the Skyhawk's impeccable reputation.
Today, the dark cloud has passed. In fact, Lycoming representatives now joke about those dark days, saying that they will never again make an engine with the letters AD in the model number. After the ADs were complied with, this engine and magneto have proven to be dependable and reliable. A number of Skyhawks built from 1977 to 1981 have had 180-hp engines installed by supplemental type certificate. This STC allows the gross weight to be increased to 2,550 pounds, in essence creating a 172Q.
According to Vref, the aircraft valuation service available on AOPA Online, Jensen's 1966 172G has a retail value of $37,321; Brown's 1972 172L is valued at $46,313; and Gibbs' 1980 172RG is valued at $74,698. Anyone having trouble justifying the purchase of a Skyhawk should compare the average retail prices of these same three airplanes eight years ago. In 1993 the 1966 172G was valued at $19,250; the 1972 172L was $23,750; and the 1981 Cutlass had a value of $51,500.
Since they're so safe, economical, and fit so many needs, Skyhawks are flown a lot. According to one airplane valuation service, an average 172 is piling up airframe time at a rate of nearly 200 hours per year, with the typical 172RG clocking more than 300 hours per year.
There aren't too many maintenance gotchas on a fixed-gear 172. Look for buckles and deformation in the horizontal stabilizer front spar. The spar is sufficiently strong for normal flight loads, but until pilots stop sitting on the horizontal stabilizer, using body weight to lift the nose gear so they can horse the airplane around on the ground, these spars will continue to be damaged. Cessna Service Bulletin SEB94-8 addresses the inspection and repair.
Early 172s repeatedly suffer broken elevator bell crank brackets. This can be detected by installing the control wheel gust lock and then attempting to move the elevator's trailing edge — if it moves more than an inch or two, inspect the bracket, which is below the floor under the front seats.
In spite of a simple airframe, a fifth-generation landing-gear retraction system, and a very good engine, 2001 has been an expensive year for Cutlass owners. Two costly ADs have come due — one requiring replacement of the engine oil pump gears (96-09-10) and one requiring inspection of the landing gear pivots for cracks (2001-06-06). In addition, the FAA issued an airworthiness concern sheet (ACS) stating that cracks in the landing gear actuator cylinder assemblies may be cause for future AD-mandated maintenance.
Both AOPA and the Cessna Pilots Association ( www.cessna.org) will be vigorously responding to this ACS. There are two other owners' groups for these models: the Cessna Owner Organization ( www.cessnaowner.org) and the Cessna 172-182 Club ( www.cessna172-182club.com).
"Nothing handles like the [Cessna] 140 I used to own, but people who fly my 172, especially if they've been flying later-model 172s, are amazed at the lightness of the controls," says Jensen, an ATP and instrument flight instructor. "This is a perfect a?rplane for us because it doesn't eat you up on maintenance or operating costs, but it sure beats driving. It's hard to beat an old 172 for general flying around."
Brown bought his 172L in January 1998. He did a lot of the refurbishment work under his local mechanic's supervision. Searching for more climb performance, Brown installed a Power Flow extractor-type exhaust system (see " Pilot Products," March 2000 Pilot) in early 1999. This increased the engine's power enough that Brown had to have the propeller repitched to keep from exceeding the upper rpm limit during cruise.
The 172RG, with its retractable landing gear and constant-speed propeller, is a complex airplane. This means higher maintenance costs and more costly insurance premiums. Many of the Skyhawks on the market have been used primarily as training airplanes, with a lot of hard training hours on the tachometer and a huge number of landings. Be ready to pay above-market prices for low-time, well-maintained models.
The first rule of airplane ownership is to buy the airplane that fits your budget. The second rule is to buy the airplane that fits your needs. The numbers prove that the Cessna 172 offers owners a wide range of possibilities. It is the most popular light airplane ever built, with more than 36,000 produced before the resumption of production in 1996.
The reasons are obvious. The airframes are durable and well know to maintenance technicians. The engines are dependable, parts and technical support is plentiful, the airplane is simple enough to be affordable — and capable enough to carry two or three people and some baggage to destinations that would take hours to reach by car.
A clean 172 is a gold-plated investment that will provide great service to those smart enough to know that dependable systems, coupled with reasonable operating costs, equal a winner. The 172 has been proving it since 1956.
E-mail the author at email@example.com.
The key to maintaining the often-maligned Cessna retractable landing gear system is a thorough knowledge of the landing gear electrical circuits. The system in the 172RG is the fifth generation of Cessna retractable systems that started in 1960 with the 210. Systems from 1970 on have all featured a self-contained power-pack system located in the passenger cabin between the firewall and the fuel selector pedestal.
The hydraulics in these systems are very simple and dependable and can be counted on for years of trouble-free service. The control circuit — consisting of the small switches that tell the power pack where the landing gear legs are and the squat switch circuit that prevents landing gear retraction when the weight is on the nose gear — is at the root of 90 percent of the problems in these systems. Owners can, with only a few hours' effort, figure out how their landing gear systems operate by studying their service manuals.
All that's required is the ability to understand simple DC electrical circuits, an understanding of what a diode does in this system (it's an electrical check valve that only lets electrical current flow in one direction), and a little time. A mechanic who knows and understands the electrical control circuits will have no trouble keeping this system in good shape. — SWE
Cessna 172RGs are all affected by a new airworthiness directive. AD 2001-06-06 requires owners to remove and inspect the landing gear pivots for cracks. If both pivots are crack-free, new bushings must be installed on each pivot assembly before reinstallation. If cracks are found, the pivots must be replaced. The initial inspection must be completed within the next 100 hours time-in-service after May 14, 2001.
The FAA estimates that the initial inspection and bushing installation will cost $1,700 if no cracks are found. If one pivot must be replaced, the cost will be $4,663; the cost to replace both pivots is estimated to be $7,626, or approximately 10 percent of the airplane's value.
?nyone considering the purchase of a 172RG should make sure that this AD has been complied with before signing the final papers. — SWE
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