Hi again, oggers.
On the certification issue, FAR 33:19, headed “Durability”, said this in 1965:
Engine design and construction must minimise the development of an unsafe condition of the engine between overhaul periods.
(I think the current FAR 33:19 still starts with that sentence.)
FAR 33.7 deals with engine operating limitations.
I’ve always interpreted these provisions, and their predecessors prior to the advent of the FARs, as having the effect that the durability standard required the engine to make it to TBO, provided the engine was operated within the established limitations, which limitations end up in the “Limitations” section of the AFM.
Otherwise, the standard and the certification are a bit of a nonsense.
It just so happens that there is no limitation in my AFM as to how long the engine may be operated at maximum rated power, and it just so happens that I can operate the engine at maximum rated power without exceeding any of the limitations such as CHT, oil temperature etc.
Indeed, I anticipate that my engine would last longer if it were operated continuously, rather than started and stopped every few hours. Cold starts are when most engine wear and tear is inflicted.
On the mixture front, I note TCM SID97-3E. It deals with fuel adjustment procedures for TCM engines. It provides for, among other things, fuel system adjustment values.
For e.g an IO-520-B the SID specifies full power fuel flows of 23.2 to 24.9 US gallons per hour. That’s a range of 1.7 US gallons per hour.
I note this because one engine adjusted in accordance with the SID can have a full power fuel flow of 24.9 US gallons per hour, another can have a full power fuel flow of 23.2 US gallons per hour, yet both have mixtures set to “full rich”. The “full rich” setting on the second engine is leaner than the “full rich” setting on the first engine.
Both engines could be set up to have full power fuel flow of 25 US gallons per hour - out of specification - but that would still be a leaner “full rich” mixture than if the full power fuel flow was set out of spec to 25.1 US gallons per hour.
When convenient:
You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT?
Real world numbers please.
[A]t what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please.
You’re the one flying all the precious passengers around each day. You must be setting the mixture
somewhere, and doing so to avoid detonation?