Aircraft safety statistics

[StSanta]

Been searching the web a bit but haven't come up with something authorative.

Had a discussion with one of our pilots. He argued that in GA having a twin engined plane doesn't necessarily add safety because the average pilot could be overloaded by an incidents and there are more things to control and more things that can break.

On the other hand, the small C-182 we operate has only one engine and if that goes out on takeoff say 300 feet above the ground, we're SOL. A twin engined plane could level off, turn around and land. Our Cessna would have to be put down immediately at the best possible spot - with 6 people in it. Only one of them wearing a seatbelt.

OTOH there was an AN-28 accident in Norway last year. Pilots overshot the runway on approach, applied power to go around only to have both engines go out at once.

Also, how does piston engined planes compare to turbine ones statistically? Which engine is more reliable? And wtf does it cost so much to stop/restart a turbine compared to a piston engine?

Oh yeah whhile I'm at it asking questions: we hve just replaced the cylinders in our Cessna - they then lost compression after about a month. I heard one of the pilots mumbling something about the engine being 'treated too nicely'. What gives?

[Toad]

Originally posted by StSanta
A twin engined plane could level off, turn around and land.

Also, how does piston engined planes compare to turbine ones statistically? ?

Oh yeah whhile I'm at it asking questions: we hve just replaced the cylinders in our Cessna - they then lost compression after about a month. I heard one of the pilots mumbling something about the engine being 'treated too nicely'. What gives?

Depends on the twin. Some of the twins struggle on one engine even when lightly loaded. I have this feeling you guys cram in everything but the kitchen sink. Heavily load some of the light twins, it might be a challenge to get it back around and on the ground.

Turbines generally are safer than pistons but cost more to operate. No free lunch; the money part of a turbine is the "hot section".

Sounds like maybe the engine wasn't broken in correctly; doesn't sound like you put a lot of hours on the rebuild. Not sure what "treated too nicelyl" would be. Just do what the manufacturer tells ya to do......... Usually when you have problems that soon after a rebuild either something was done incorrectly or there may have been another problem that didn't get addressed.

[Holden McGroin]

Originally posted by Toad
Depends on the twin. Some of the twins struggle on one engine even when lightly loaded.

According to my local FBO, (who operates an old Aztec) on one engine, his Piper Aztec will fly you in perfect safety to your crash site.

[Toad]

Exactly.

[Maverick]

In any twin engine aircraft if you go below minimum single engine controlable airspeed you are going down. If you have sufficient altitude to trade for speed you may regain control IF the single engine has enough power to maintain the speed and altitude. If the engine cannot develop enough power to maintain altitude the result is forgone. You are going down. Where the impact or landing happens depends on where you are flying. If there is a field nearby you might make it. No matter what, the remaining engine will get you to that point where you run out of air beneath the wings.

Some twin pilots got into the frame of mind that the single engine would be enough to carry them and became convinced otherwise when all the other options for landing sites were no longer available.

As to the cylinders losing compression. If the engine was not broken in properly the rings never seated to the cylinders. The cylinders could also have become glazed. In any case there is insufficient seal by the rings to maintain compression. That means you are losing horsepower.

Normal break in for small engines is to get it up to about 75% power and hold it there until the rings seat. It can generally be seen when the cylinder head and oil temp. drops at that power setting with no change in mixture.   It can happen in one hour, it may take 10. In the case of the engine I built(Cessna 172) it took about 6 and a half. Very boring to bore circles in the sky staying in gliding distance of the field. I did the flying, I built it I put my butt on the line for it. Spooky as hell on take off. You keep running through the rebuild in your mind on taxi wondering "did I do everything right"??????

[Chairboy]

The guy who owns the FBO I rent from also has an airframe certificate, one good way to avoid hemorhaging money in aviation.  He just put a new cylinder on the Piper I fly, and they're using mineral oil to help get the rings to seat properly.

A question, you mention that the C-182 you fly only has one person belted in.  Are you carrying skydivers?  I'm studying for my written, and I recall that FARs say that everyone needs to be belted in during taxi, takeoff, and landing.  It doesn't mention specifically whether or not parachutists are exempt from this, but that's the closest I can guess.  How's that work?

[cpxxx]

There is a saying. 'If the engine fails in a single you crash immediately but if an engine fails in a twin the other engine allows you fly to at airport and crash there. '

Yes, chairboy skydivers are not strapped in. I certainly wasn't when I made my jump.  Not only that there's usually a gaping hole where the door used to be.  I met many skydivers who hate to fly with out a parachute.  They jump at the smallest provocation. There was a famous incident where a skydiver became a pilot and on one lift, stalled the plane, panicked and bailed. Much to the surprise of his colleagues in the back. Who naturally followed him out the door.  I would love to have been a fly on the wall when that matter was discussed on the ground.

[beet1e]

Santa - the other guys said it...

I believe your new cylinders would have had a criss-cross pattern cut into the wall to retain oil. It's like that because there's no way to machine a cylinder to be a perfect fit for the piston that goes inside it. The cylinder bore will actually end up being slightly ovoid in section, owing to the sideways forces exerted by the crank arrangement.

Unlike a car, where the advice is (or was, in decades past) to baby the engine, in an aircraft engine it's the worst thing you can do. The engine needs to be worked hard so that the pressure in the cylinders forces the piston rings against the cylinder walls so that they can wear away the criss-cross oil retaining grooves. Like Mav says, if you baby the engine, the pressure in the cylinders will be inadequate to force the piston rings against the cylinder walls. Oil will get past the piston rings and will form a glaze on the cylinder walls. Oil consumption may be excessive, and you won't get proper compression. Engine strip down is a likely next step.

Next time you fly with a new engine, work that engine - hard!

[ChickenHawk]

Originally posted by StSanta

Had a discussion with one of our pilots. He argued that in GA having a twin engined plane doesn't necessarily add safety because the average pilot could be overloaded by an incidents and there are more things to control and more things that can break.
 

Here's a NTSB report on a P-38 that didn't make it after a loss of power in one engine.

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001208X08240&key=1

[cpxxx]

I think the pilot of that flight was Jeffery Ethell. The well known aviation author. I think. It fits with the timeframe.  Very unfortunate. The P38 was and is unforgiving when it loses an engine.