Reliability of Aircraft Engines

[Bazile]

There was a time when passenger aircraft had to have four engines to cross the atlantic - now aircraft with two engines are normal . Is any one else amazed by their reliability , given all the parts contained within them ? . If your car engine develops a fault - you can push it to the side of the road and call out a breakdown service. If an aircraft engine develops a serious fault , up there........ well , you can see what I am getting at .

[Clanad]

All aircraft with less than three engines are required to meet extensive testing for extended flight overwater. Called ETOPS, ( (Extended Twin Engine Operations). The airline is granted greater and greater times as the testing progresses. At first, the airline is required to fly routes that are no farther than 120 minutes from a suitable landing place (the time is based on airpeeds on one engine). If the testing goes well then 180 minutes is granted. As far as I know 240 minutes is the greatest amount of time granted so far... Additionally, jet engines actually have fewer moving parts than the old compound supercharged engines on DC-7's, Lockheed Constellations, etc... They were an engineers nightmare. The design goal for the old "round" engines was one horsepower per pound. That was never achieved but the designers came very close.

[ianess]

The jet engine is a relatively simple machine which is ultra-reliable, for example as shown by Steve Fosset twice circumnavigating the globe nonstop with just the one engine.
I think the Boeing 757 was the first airliner allowed to fly directly across the Atlantic without requiring to be within 2 hours of a landing strip.
Jet technology is nearly 70 years old now........Concorde has been and gone with nothing to replace it.......is it not about time we were going at warp speed?

[alvin100]

The technology certainly exists to make much faster aircraft.
Its certainly not the engines that are the limiting factor, Amongst other things its down to cost, fuel economy, servicing, as well as noise from engines and sonic booms.
About 600mph is the current speed for most big Jets, Increasing it to 800mph wouldnt make that big a difference to your overall journey time to say the USA but it would increase, noise and costs considerably.

[pagey]

i service a machine that has a motor that starts and stops every 10 mins, and has been doing so, in many cases, for up to 10 years. I was amazed by this, and likewise, aircraft engines and props.
The thing that amazes me about planes (especially transatlantic ones) is that they are nearly always in the air as well! The chance of an engine failing whilst in the air is so much higher than whist on the ground!
A friend of mine engineers advanced propellors, and the tests they go through are unbelievably rigorous. This gives me every confidence in the designers and engineers that have put these things together.

[Bazile]

It surely is a testament of engine reliability - that there are aircraft that are allowed to be 4 hours away from the nearest landing strip .

Incidentally , why are prop shaft engines still used on new aircraft as opposed to jet engines - is it because the former is more efficient at certain operating heights ?

[ACB312]

Pagey - why does it amaze you that transatlantic planes are so often in the air? A plane doesn't make money on the ground. Also, what's your logic in thinking jet engines are more reliable on the ground rather than cruising at an optimum altitude? I'm not wanting to appear cheeky here - just questioning your logic. Cheers, Andy

[Bazile]

I think the point pagey is making is that he is amazed by their reliability , given that the aircraft are constantly airborne and that the probability is that if an engine is going to develop a fault , it will most likely be when it is in the air .

no doubt pagey will confirm , or otherwise

[pagey]

ACB, I was just stating that given the plane is in the air most of the time, it is therefore more likely to fail at a time when it is in the air.

There's always logic. Feel free to question it!