Low CHT and Oil Temp before starting

[Scott - A2A]

This is on the TO DO list for the next update.

Scott.

[Jarek]

I have no idea how it is implemented/planned, but as the base for this interesting discussion I would like to bring here some ideas how it could be done. The assumption here is that A2A team collected some CHT/Oil Temp. samples during test flights. Based on this, data for normalized conditions can be calculated and then used to approximate CHT for any OAT.

Very interesting studies about CHT and Oil temperatures were done by Kevin Andrew Stuth, student at College of Engineering at
Florida Institute of Technology in his thesis. Measurements were done on Piper Seneca (with smaller engine, no cowl flap), and some most important findings are presented below. I believe the best idea would be to take Bonanza on a same ride with conditions described there to check what results will be produced.

The envelope for CHT could be estimated from FAA regulation CFR 14, Part 23, Subpart E, Section 23.1043
https://www.law.cornell.edu/cfr/text/14/23.1043#a_1
which says:

(c)Correction factor (except cylinder barrels). Temperatures of engine fluids and powerplant components (except cylinder barrels) for which temperature limits are established, must be corrected by adding to them the difference between the maximum ambient atmospheric temperature for the relevant altitude for which approval has been requested and the temperature of the ambient air at the time of the first occurrence of the maximum fluid or component temperature recorded during the cooling test.

So the formula is:

Tc,faa= Tr + [100 - 0.0036Hp - Ta]
where:
Tc,faa = FAA predicted temperature of engine component or fluid with ambient atmospheric conditions equal to 100F at sea level.
Tr = recorded maximum temperature of engine component or fluid during test
Hp = pressure altitude of aircraft at time Tr was recorded
Ta = ambient air temperature at time Tr was recorded

with known datapoints and having Tc,faa, we can approximate Tx - CHT temp. for given OAT < 100degF:

Tx = Tc,faa - [100 - 0.0036Hp - Ta]

The assumption here is that CHT peak vs OAT is at 100degF. This is very conservative approach and produces results which are higher than normally measured and is questionable by both sources provided below.

For anyone interested in diving in the details, link to source material is here: https://repository.lib.fit.edu/handle/11141/1138.

Same subject, but tests of 6-cylinder Piper Saratoga: Juan Carlos Valer, "A Study of the Temperature Correction Methods for Reciprocating Engine Flight Testing under nonStandard Conditions" https://trace.tennessee.edu/cgi/viewcon ... k_gradthes, University of Tennessee - Knoxville, 2003.

[Scott - A2A]

Just an FYI, this has been fixed for the next update.

Scott.

[Piper_EEWL]

Just an FYI, this has been fixed for the next update.

Scott.

That’s good news Scott.

Thank you!