Engine theory

[funfly]

When I did my exams x years ago I questioned what good it was learning all about two and four stroke engines and having to take an exam about same when the opportunity to get out and tinker with them while actually flying was a bit limited.
The general reply was that you had to understand how the donkey works in case you needed to diagnose a problem when flying etc.
When converting to injection, diesel and jet engines a 'type' approval must obviously be obtained to fly these but, as I understand it, no theoretical examination on the workings of these is mandated.
Does the importance of understanding how an engine work disappear when a different type of motor is substituted?

[Whopity]

If you are completing a Type rating then there is a theoretical exam associated with that type. It is set by the FTO or TRTO conducting the training and will include questions on engines and other aircraft systems. For multi-pliot and high performance types you are required to have passed the professional technical exams relevant to type.

You can fly a diesel with just differences training but its still a reciprocating engine.

[DFC]

To add to what Whopity says, If you are SEP rated and what to fly a Diesel powered SEP then the engine theory element has to be provided during the differences training by the instructor and they need to check your understanding.

While during your basic PPL training your Authority based written exams may have been limited to piston training, if you had presented in a diesel aircraft for the test the examminer will have given you some oral questions regarding the engine.

At PPL level, type / class specific questions are covered during the GST.

[BillieBob]

What Whopity said plus - Standards Document 34 states:

"The PPL theoretical knowledge syllabus does not include any training or testing in the theory of turbine engines. TRTOs providing training to PPL holders for a first turbine-engined aircraft type must include in the theoretical knowledge syllabus training in basic turbine engine theory."

Which seems to cover most eventualities.

[lasseb]

I don't think there is any requirement for a difference training if you want to fly diesel a/c. There is only requirement for familiarization which you may do yourself without any instructor.

However, most of the diesel aircraft's out there (like Diamond) uses a single thrust lever system, and this requires a difference training by an instructor.

[BillieBob]

lasseb, you are quite right, I don't know what I was thinking when I wrote my previous post. Differences training is, of course, not required between diesel and petrol engined SEPs.

MODs - we currently have three separate threads running on differences training, two of which are related to diesel engines. Combine?

[SNS3Guppy]

Does the importance of understanding how an engine work disappear when a different type of motor is substituted?

The importance of understanding how your aircraft works, not just the "motor," never goes away. Systems knowledge is far more than theoretical rubbish.

In the case of your piston power plant, understanding the operational theory is basic to understanding leaning, carburetor ice, manifold pressure and it's applicability to setting power, fuel flow, the impact of a constant speed propeller, etc. These, in turn, have direct bearing on the handling of abnormal and emergency situations.

In a fuel injected Continental IO-520 in a Cessna 206, for example, one may see a high fuel flow, and feel that one should retard the mixture in flight. At first blush, this appears the right choice, to bring fuel flow back to an acceptable value. The problem is that if one understands the fuel flow indication system in that airplane, one will know that fuel flow is determined by the pressure drop across the fuel injector nozzles. A plugged injector means a lower fuel flow, which indicates as a higher fuel flow. At high power settings, where the greatest disparity will occur, retarding the mixture is exactly the wrong thing to do; one may well damage the engine, or cause it to fail. In this case, knowing your system may be critical to your health.

As you can see, there's a lot you can do in the cockpit about engine problems, whether it's the way you address them, or the checklist you choose.

Systems knowledge, whether it's your engine or your electrical system, is always important. This is true whether you're flying a Cessna 152 or a Boeing 747.

[Biggles78]

Originally Posted by SNS3Guppy

one will know that fuel flow is determined by the pressure drop across the fuel injector nozzles. A plugged injector means a lower fuel flow, which indicates as a higher fuel flow

It's been 28 years since I sat A/C Tech so please excuse the request for claification. Apologies to funfly for the "slight" thread hijack.

Thanks for my education lesson for today. I had either forgotten or never knew that was how fuel flow was measured. I now need to do more reading on this subject.

If I understand what you said correctly, because the blocked injector will not result in the lower pressure because the fuel is NOT actually flowing, this is then displayed as a higher fuel flow even though it is not. Does the same anomaly occur in the Lycoming IO-540 or indeed all IO engines? I ask because it seems that this appears to be due to the way the instrument interperates the pressure and displays it as a higher fuel flow. Is this somewhat correct or am I talking through where the EGT sensors are located?

Gotta love EGT gauges that able you to cross check and make sure fuel flow matches with the appropriate temps.