Cessna Single-Engine ADs: What's Going On?

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EDITORIAL. The Priority Letter ADs against 172R and 182S mufflers is just the latest of a string of highly-publicized Airworthiness Directives against the new Cessna Skyhawks and Skylanes. Previous ADs and Service Bulletins required inspection for missing rivets in the forward door post structure, and modifying the Skyhawk engine cowling to prevent interference. Why this rash of glitches, and what does it mean? We think there are at least three important lessons here.

ATISWhile most of us were busy unwrapping Christmas gifts and ringing in 1998, executives at Cessna's single-engine plant in Independence, Kansas, were preoccupied with a rather distressing situation. They'd just learned that the Aeroquip-built mufflers installed in hundreds of brand new Cessna 172R Skyhawks and 182S Skylanes had potentially defective welds that could allow carbon monoxide contamination of the cabin via the cabin heat system.

The news could hardly have come at a worse time. Cessna was basically shut down for the holidays, and key staffers had to be called in on an emergency basis to evaluate the seriousness of the situation and come up with a fix...fast! The problem was first spotted in a new 182S on a late December delivery flight. The FAA decided to issue Priority Letter Airworthiness Directive 98-01-14 on December 30th, grounding the 19 affected Skylanes until their mufflers could be replaced.

Then, Cessna and the FAA realized that a similar problem might exist in the 172R, and hastily-arranged pressure testing of 25 new Skyhawk mufflers confirmed their worst fears: 5 of the Aeroquip-built mufflers had leaky welds. This represented a much more serious problem, because more than 300 new Skyhawks had been delivered to customers, and it would take months to build enough replacement mufflers to retrofit the fleet. After some quick negotiations, the FAA agreed not to ground the airplanes if their cabin heat controls were safety-wired "off" until the suspect mufflers could be replaced. This was small consolation to owners of new Skyhawks based in the northern latitudes, of course.

1997 Cessna 172ROn January 9th, the FAA issued Priority Letter Airworthiness Directive 98-02-05 requiring immediate inspection of the 172R fleet before further flight, and the safety-wiring of cabin heat controls on those airplanes found to have Aeroquip mufflers. The AD gave owners 50 hours or 6 months to replace the mufflers. Meantime, Cessna went into high gear to build 300 or so replacement mufflers as quickly as possible, and instituted a "triage" system so that the limited quantity of mufflers that were available would go to where they were needed most (i.e., owners in cold-weather areas).

So many glitches, so little time

The muffler woes are just the latest in what seems like a shocking string of sweeping actions against the new Independence-built Cessnas. In June, the FAA issued an Emergency A.D. against the entire Cessna 172R fleet (which at the time numbered only 76 airplanes) as a result of an incident that occurred during a ferry flight of a new Skyhawk to Europe. The pilot launched from St. Johns, Newfoundland, with several hundred gallons of fuel in ferry tanks, but quickly became concerned that fuel consumption was much greater than normal, and turned back. The engine quit from fuel exhaustion one-half mile short of the runway at St. Johns, and the pilot dead-sticked it in to a safe landing. Investigation revealed insufficient clearance between the cowling, the exhaust tailpipe, and the gascolator drain standpipe. Apparently the engine rocked on its shock mounts (possibly during starting), causing the tailpipe to hit the cowling, the cowling to rock on its shockmounts, and to contact and shear off the gascolator drain. The resulting Emergency AD required enlargement of several cowling openings, including those for the tailpipe and gascolator drain.

Then in September, an FAA inspector toured the Independence plant and discovered some rivets had been omitted from the lower forward doorpost structure of Skyhawks and Skylanes on the assembly line. The result was that on September 15th, Cessna issued sweeping Service Bulletins against the entire 172R and 182S fleet (at that time, 135 Skyhawks and 27 Skylanes) calling for a gruelling 14-man-hour disassembly inspection and beef-up of the doorpost structure. Owners were given six months to comply. A week later, after some intense behind-closed-doors meetings with the FAA, Cessna decided to suspend further Skyhawk and Skylane deliveries until the Q/A problems could be fully addressed. Skyhawk deliveries resumed  ten days later, and Skylane deliveries two weeks after that in mid-October.

Two months later, the leaky muffler situation came to light.

Common thread?

This recent rash of problems with Cessna's new singles naturally prompts the question "what do these problems have in common?" The answer, as best I can determine, is "not much."  Let's take a closer look.

The June problem involving Skyhawk cowling interference was not a quality control problem. It was an engineering problem...and an understandable one at that. Prior to the St. John's fuel exhaustion incident, 172R's had amassed many thousands of problem-free flight hours. It was probably impossible to foresee that a highly-improbable worst-case combination of manufacturing tolerances plus an unusually large movement of the powerplant on its shock mounts (possibly as a result of a backfire while starting) resulted in the tailpipe contacting the cowl and the cowl shearing off the gascolator drain. It's almost impossible to foresee problems like this. The resulting Emergency A.D. was the first against the new Cessnas, and for the folks at Cessna's single-engine division it was undoubtedly as distressing as that first scratch on a new car. But like that first scratch, a first A.D. was inevitable. Cessna and the FAA did what they had to do to make sure this highly-improbable chain of events will not recur.

The September discovery of the missing doorpost rivets was an entirely  different matter. This clearly was a quality control problem at Cessna, and Cessna clearly took rather drastic measures (a highly visible suspension of deliveries plus not-so-visible retraining of factory workers) to address it. Cessna clearly underestimated the difficulty of properly training its workforce during the rapid ramp-up of production at Independence, and the September episode caused them to re-evaluate their plans to accelerate production. Interestingly enough, although I view this as being by far the most serious of the three problems under discussion, it was also the only one that did not result in the issuance of an Airworthiness Directive. That's because the FAA agreed with Cessna that the missing doorpost fastners threatened only the longevity of the aircraft, not safety of flight.

The December muffler problem was also a quality control problem, but it was Aeroquip's and not Cessna's. Only 19 of the 70-odd 182S Skylanes had potentially leaky Aeroquip-built mufflers; the rest had Cessna-built mufflers that did not leak. Aeroquip has been a major aviation supplier for decades and was not new to the exhaust component business, so Cessna had no reason to suspect that the company might be furnishing unsafe mufflers. Of course, whoever was at fault, Cessna is ultimately responsible. Although the FAA saw fit to issue Emergency ADs requiring immediate compliance, one could well argue that this was something of an overreaction. As best I can determine, there was never a documented case of carbon monoxide contamination of the cabin air as a result of these Aeroquip-built mufflers. The leaky welds were detected only when the mufflers were pressure-tested at five to ten times normal operating pressure. Although there's no question that the situation had to be addressed once it was discovered, a more relaxed compliance time (coupled, perhaps, with the requirement to put a CO detector button in the cockpit) might have been an appropriate response to the actual threat.

Lessons learned

Although there does not seem to be a common thread connecting these three problems with the new Cessna singles, I do think that some observations are in order. Three lessons come to mind:

  1. We're living in a post-ValuJet era in which the FAA Flight Standards folks don't seem to have much of a sense of humor, to put it mildly. The FAA took an incredible amount of heat last year for failure to report or act on known problems, and generally for "being in bed with the industry." Well, no more. It's pretty clear that the FAA is breathing down Cessna's neck in Independence these days, and I sincerely doubt that Cessna is the only aircraft manufacturer under the microscope. Seems as if everyone in the aircraft manufacturer food chain from Boeing on down is under renewed FAA scrutiny these days. I fear that Admiral Busey's "kindler, gentler FAA" is will soon be a fond but distant memory, and that the needle is swinging towards strict compliance and enforcement. God help us all.

  2. When Cessna decided to get back into the single-engine airplane business after a decade-long hiatus, there was intense pressure from many quarters for them to start producing a clean-sheet, state-of-the-art aircraft instead of the stodgy high-wing strut-braced Skyhawk and Skylane. In hindsight, it seems to me damned fortunate that they didn't. Cessna wisely recognized that the challenges of starting up production and training a new workforce were daunting enough, without also having to deal with the inevitable problems of a new aircraft design. Given the problems that have arisen just building plain ol' 172s and 182s, just imagine what might be going on if Cessna had decided to build the composite, glass-cockpit, fly-by-wire airplane with FADEC-controlled Dynacam engine that so many folks urged them to produce!

  3. Here's something to ponder: if a veteran, experienced, politically-astute, deep-pocketed aircraft builder like Cessna is going through this kind of aggravation building simple aircraft like the 172 and 182, just imagine what still-wet-behind-the-ears manufacturers like Cirrus Designs, Glasair and Lancair are likely to encounter as then enter the wonderful world of certificated aircraft, product liability and FAA oversight. I sure hope they have a closet full of flack jackets and a drawer full of MIL-SPEC titanium underwear.