Patrick wrote:
When I first started flying in Germany, I was taught indeed to point the nose in the general direction of the wind if practicable. We would then point into the approach after the run-up to check for traffic, essentially zickzacking from left to right or vice versa at the holding point.
“My” flying school is based at an international airport, together with another flying school (which has trained some contributors on this forum…). There is no way that we first point our nose in one direction for the engine run-up and then turn around the other way to look for traffic. There are aircraft in front and behind us. One engine, two engine, turboprop, jet. You stop where you stop, do your things and taxi into the runway when instructed. Nobody ever performed this kind of circus here (and if so only once…) and we all live to tell the story as do the engines of our planes.
what_next wrote:
There is no way that we first point our nose in one direction for the engine run-up and then turn around the other way to look for traffic. There are aircraft in front and behind us.
That’s what I meant with “if practicable”. This wouldn’t occur to me at an international airport with any sort of traffic, obviously. Checking for landing traffic before entering the runway is also maybe slightly less imperative at a controlled airport than at an uncontrolled field – although it certainly doesn’t hurt to visually double-check there is no big or small iron on short final. 
I guess it’s also a question of local practices. At EDLE I do this, most of the training aircraft do this as well I’d say. There isn’t any downside to it, either.
what_next wrote:
“My” flying school does (unfortunately) not operate a C172 any more (only 1C52 and Pa28 and Pa44) but the first C172 POH that google found for me ( https://takewingaviation.com/wp-content/uploads/2017/02/N739EF_172N_POH.pdf ) does not say that the engine run up must be made facing into wind (page 30). The only thing that might be interpreted in that way is this bit under “Warm up”: Since the engine is closely cowled for efficient in-flight engine cooling, precautions should be taken to avoid overheating during prolonged engine operation on the ground.
Sorry, you are right. It’s in my plane’s (Z142) POH (p. 4-9, “Perform the ground check with aircraft heading into wind.”) and got confused by a quotation on a web page that appeared to be from the C172M POH, but it was not.
IMO, it has little to do with the engine itself.
But during these checks, especially if you include the pre-takeoff checks, you will be sitting there for a few minutes, maybe half a minute with the engine power.
If you face with the tail into any significant wind, you will have the elevator and ailerons banged against the stops unless you hold them quite tight. So in general, it is beneficial, not essential, to face into the wind.
Overall – if I have the opportunity to face into the wind – great. If not – no big deal, but better have a firm hold on the yoke / stick.
Cobalt wrote:
If you face with the tail into any significant wind, you will have the elevator and ailerons banged against the stops unless you hold them quite tight. So in general, it is beneficial, not essential, to face into the wind.
Who does a runup without holding the yoke/stick tight? I just can’t imagine doing it.
For an LAA permit check you do the engine rpm checks with no more than a light sidewind – presumably to avoid a headwind changing the RPM values. Lots of aircraft have the propellers mostly stalled when the aircraft is immobile, so perhaps a headwind that was just sufficient to un-stall the propeller tips might change the static RPM considerably?
I can’t imagine feeling comfortable doing a run-up with a substantial side-wind, but I was taught to take other factors into consideration – e.g. will there be a runway incursion if the brakes fail? What’s behind me?
I’ve heard about this, but was never taught it myself and it isn’t practised in my club.
So far three possible reasons have been suggested:
• For engine cooling
• To avoid “banging” control surfaces
• To get the correct static rpm
None of these make sense to me. During the short time it takes to do an engine check (certainly less than 30 seconds), there is no possibility of overheating the engine.
“Banging” of control surfaces is just as much a problem when you are taxying to the runway with a tailwind. What would be the difference during the run-up?
Certainly the static rpm can be affected by the wind, but various amount of headwind would also mean different static rpm. If anything, a headwind would be detrimental as it would increase the static rpm so that you would possibly do the run-up at too low a power setting – meaning that ignition problems would be less evident.
What does matter, if there are several aircraft in line for takeoff, is to do the runup at a slight angle to the taxiway to avoid hitting the aircraft behind you with the propstream.
Might this be a holdover from liquid cooled WW2 days? Time on the ground was limited before overheating problems occurred. Conventional aircraft tend to be happier pointed into wind.
It may fall in the same category to cycling the propeller several times, which is not ideal for the crankshaft, and this I understand may be a holdover from the 1930/40’s when cycling the prop ensured the governor had fresh warm oil. Someone may find a Lycoming document which calls for just one cycle for modern (quote-unquote) engines.
RobertL18C wrote:
It may fall in the same category to cycling the propeller several times
Perhaps that depends, “proving” the props are going to feather is a potential life saver in a twin.
Fuji_Abound wrote:
Perhaps that depends, “proving” the props are going to feather is a potential life saver in a twin.
Do you need to do it three times to prove it or would once be sufficient?
