So, what do I have against certified engines anyway? Nothing really, except the cost. I used to blame the manufacturers for the high cost, but I suppose that it’s really the lawyers we should blame. Everyone who loves general aviation owes Lycoming and Continental a debt of gratitude. It can’t be an easy business, surrounded by underemployed lawyers on one side and the FAA on the other it is impressive they have stayed in business at all. You also have to admire the product. In general those engines are simple, light weight, reliable and very well suited to the purpose.
But we, in rotary aviation, have found something better. Thanks to the miracle of "Amateur Built," we are able to take advantage of it. The rotary is even simpler and lighter weight than those certified engines that have endured the test of time so well. More importantly, the rotary has internal components that are nearly indestructible under normal use. There is a much larger margin of safety between normal operating forces and destructive forces than what you find in piston engines. This means no more restriction to 70% power for cruise. The rotary can easily handle moderate turbocharging without significantly affecting the "TBO" or the overall reliability of the engine, all at a fraction of the cost. Maintenance and rebuild costs are especially low compared to certified engines.
The metamorphosis of the rotary into the leading aircraft engine will be a long one. There will no doubt be in flight failures and other set backs. But one thing is for sure, no rotary powered aircraft will ever come down because of a broken crankshaft, broken valve stem, or cracked cylinder head - all of which are common causes of certified engine failure.
So why this page? Most people who don't know any better think that we, in rotary aviation, are trading some safety for a few thousand dollars. This is my way of pointing out that their golden standard, the certified engine, is far from perfect. I welcome submissions (the list here is very short), comments corrections via e-mail. And remember, the vast majority of general aviation crashes are caused by pilot error - these are the exceptions.
After the list of recalls, I searched a SINGLE, randomly selected month (November 1995) in the NTSB reports and selected out accidents caused by primary engine failure. This does not even include engine failures that did not cause an accident. I have no guess as to how many of those exist for a given period of time, but there are no-doubt many. Essentially, none of those failure modes are possible with the rotary engine.
Latest Crankshaft Recall by Lycoming: (2005)
MORE SUSPECT LYCOMING CRANKS
Lycoming is casting its recall net a little wider for engines with potentially faulty crankshafts and the FAA is reinforcing that with yet another proposed AD. Since 2002, Lycoming has replaced hundreds of cranks containing suspected metallurgical faults and now nearly 400 more have been added to the list. In a Nov. 30 supplement (check there to see if your engine is affected) to a mandatory service bulletin issued last July; Lycoming said a single failure (no accident involved) prompted the expanded recall. The Notice of Proposed Rulemaking issued by the FAA on Jan. 6 duplicates the company's call for the affected engines to be repaired within 50 hours or six months, whichever comes first. The MSB supplement and NPRM affect (L)O-360, (L)IO-360, and AEIO-360 models. Most of this batch of 391 suspect cranks went into 308 engines manufactured by Lycoming. Some of the remainder may have been used in overhauls or may be sitting on stockroom shelves. The FAA says its NPRM affects 282 engines in service in the U.S. and the types of aircraft affected range from Cessnas, Beeches and Pipers to some obscure European and Asian aircraft and even a couple of blimps. Here is a link to the full article.
> ANOTHER CRANKSHAFT RECALL -- THIS TIME, IT'S LYCOMING... (Feb 2002)
> At least four crankshaft failures in big turbocharged Lycoming engines-- at least two of them in new Cessna T206H airplanes -- have prompted Textron Lycoming to issue a recall of TIO- and LTIO-540 engines rated 300 hp or higher. Textron Lycoming Mandatory Service Bulletin No. 550 presently applies to about 400 of these engines, identified by serial number. It requires that the affected engines be returned to the Lycoming factory for crankshaft replacement within the next 10 hours of operation, with the cost (including engine removal and replacement) being picked up by Lycoming.
By PETER PATRICK -
Why did these people have to die?
Aviation authorities will investigate an engine recall announced 16 days
before a Whyalla Airlines plane plunged into the
Aviation authorities worldwide became aware of crankshaft problems in early May when Teledyne Continental Motors announced it would inspect up to 3000 engines at a cost to the company of $20 million because of faults in its manufacturing process that could lead to catastrophic engine failure. Continental announced the inspection would include all crankshafts manufactured from steel that came from a particular supplier during the two-year period from April 1998 to March 2000.
Accident Date: 11/04/95 - Report adopted on: 02/14/1996 - NTSB Accident ID: MIA96LA018 - Place of Accident: WAUCHULA, FL - Aircraft Make/Model: BOEING E75N1 - Aircraft Damage: Substantial - Engine Make/Model: CONTINENTAL W670A
Accident Narrative: THE PILOT WAS IN CRUISE FLIGHT AT 1,500 FEET AGL WHEN THE AIRPLANE EXPERIENCED A TOTAL LOSS OF ENGINE POWER. THE PILOT MADE A FORCED LANDING TO THE ONLY AVAILABLE LANDING AREA. ON LANDING ROLLOUT THE AIRPLANE COLLIDED WITH A DITCH AND NOSED OVER. EXAMINATION OF THE ENGINE ASSEMBLY REVEALED THE SERRATED TEETH ON THE VALVE TIMING GEAR AND THE INTERMEDIAT CAM GEAR WERE WORN, PREVENTING THE VALVE TRAIN AND GENERATOR FROM OPERATING.
Aircraft Make/Model: SNOW S2C - Aircraft Damage: Substantial - Engine Make/Model: P & W 1340 AN-1
Accident Narrative: THE PILOT REPORTED THAT DURING AN AERIAL APPLICATION SPRAY RUN, THE ENGINE BEGAN TO RUN ROUGH AND BACKFIRE. THE AIRPLANE WAS UNABLE TO MAINTAIN ALTITUDE AND THE PILOT MADE A FORCED LANDING TO AN OPEN FIELD. PRIOR TO TOUCHDOWN, THE PILOT PULLED THE AIRPLANE UP TO MISS A DITCH. THE AIRPLANE STALLED AND THEN LANDED HARD. POSTCRASH INSPECTION OF THE ENGINE REVEALED A CRACK IN THE HEAD ON THE #5 CYLINDER.
Accident Narrative: During cruise flight, the pilot noted a loss in engine RPM and oil pressure at the same time. He performed an emergency landing on a frozen lake. During the landing roll, the right wingtip struck a spruce tree, and the airplane was substantially damaged. During an examination, the accessory section of the engine did not rotate, when the propeller wa turned by hand. A teardown of the engine revealed that the crankshaft was fractured at the number 3 short cheek, betwee the number 2 rod bearing and the number 2 main bearing. The engine contained numerous fragments from the number 2 main bearing. The number 2 bearing saddle was severely worn and deformed. Other bearing saddles exhibited scoring. A metallurgical examination of the crankshaft revealed a fatigue failure at the aft radius of the number 2 main bearing journal adjacent to heavy rubbing marks from the number 2 main bearing.
Accident Narrative: During flight the engine started to smoke, and then it quit. The pilot immediately turned towards a known field and made an emergency landing. While landing, the propeller stopped in the vertical position and caught on the uneven terrain resulting in the aircraft nosing over. Postcrash examination of the engine revealed a cracked crankshaft.
Accident Date: 11/26/95 - NTSB Accident ID: NYC96LA028 - Place of Accident: SOUTHBRIDGE, MA - Aircraft Make/Model: STINSON 108-2 - Aircraft Damage: Substantial - Engine Make/Model: FRANKLIN 6A4-165-B3
Accident Narrative: During cruise flight, the pilot observed a loss of engine power. He performed emergency procedures; however, the engine continued to lose power. The pilot made a forced landing during which the airplane collided with trees. Postaccident examination of the engine revealed the engine crankshaft was separated into three pieces. An inspector stated, "The failed crankshaft has evidence of a fatigue fracture...."
Accident Date: 11/30/95 - NTSB Accident ID: FTW96LA061 - Place of Accident: EADS, CO - Aircraft Make/Model: CESSNA 182Q - Aircraft Damage: Substantial - Engine Make/Model: CONTINENTAL O-470-U
Accident Narrative: WHILE IN NIGHT CRUISE VFR FLIGHT, THE PILOT HEARD A LOUD NOISE AND THE ENGINE LOST POWER. THE AIRPLANE SUSTAINED SUBSTANTIAL DAMAGE DURING THE ENSUING FORCED LANDING. ENGINE DISASSEMBLY DISCLOSED THE NUMBER 2 CYLINDER HAD SEPARATED FROM THE CRANKCASE AND THE PISTON WAS FRACTURED IN TWO PIECES. THERE WAS EVIDENCE OF CYLINDER ROCKING AND FRETTING. ONE THROUGH-BOLT PENETRATED THE COWLING, FOUR STUDS WERE BENT AND TWO STUDS WERE MISSING. ONE OF THE CONNECTING ROD BOLTS WAS STRIPPED AND THE OTHER HAD FAILED IN TENSION. THE NUMBER 5 CYLINDER WAS SCORED AND THE PISTON WAS ERODED. THERE WAS EVIDENCE OF HIGH HEAT DISTRESS. THE ENGINE WAS OVERHAULED IN JANUARY 1992, AND RECEIVED A PROPELLER STRIKE INSPECTION 7 MONTHS LATER. ENGINE TOTAL TIME WAS 3,301 HOURS, AND TIME SINCE MAJOR OVERHAUL WAS 1,498 HOURS.
As for me, I'm trying to figure out what engine to put into my FT. I have an IO-540, but really want to go with a better engine. I just had a bearing fail in my Cherokee 140 after 500 hours since major and the $15k repair bill had me sell it as is to the mechanic. Time to be in control of my own engine package. The 20B would be nice, but I'm still on the fence between the 20B and some sort of other piston conversion.
-Eric Holmberg Express FT
You won't find anything near the same durability and power to weight ratio of the 20B.