I’m curious as to why the flaps are in the down position for the engine startup procedure.
Is it to prevent someone from walking up under the wing from behind?
This is the relevant page in my C172 P model POH (which is earlier than the C172R in the game and doesn’t have fuel injection), but it’ll give you an idea of what Cessna thinks the startup procedure should be.
It’s on the 172 R/S checklist.
- Preflight - extend full
- After start - Up
I’ve wondered in the sim and I recently took a first flight (172R) and observed the instructor doing the same thing.
Ok. Weird. I don’t know then. Extending them is part of the C172P preflight, so that you can check them during the preflight walk-around inspection, but they are to be retracted again at the end.
Maybe, as a wild guess, it is to ease the load on the battery? (i e. Don’t retract them until the alternator is on and charging?)
There is no special reason. It’s just how it happens in the normal flow. You extend them during preflight to inspect the hinges and then leave them like this. The next time you have power is after engine start. Technically, you could retract them as soon as you turn on the battery, but the POH prefers to save it and use the alternator.
Ah, pre-flight and alternator makes sense! That’s a big part of what we miss out on in the sim.
I like know the why to everything, it makes it easier to learn.
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For the preflight you extend them FULLY. In the sim they are set to position 1 (10 deg) and I assume it’s done because it’s the takeoff position (or better one of them). You can takeoff with flaps up and flaps 10 but the devs decided to set them every time which is actually nonsense. It’s a 172, you’re happy to have less drag most of the time.
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That’s right. It looks like a pattern carried from other (larger?) aircraft that any takeoff should always be performed with some takeoff flaps setting (other than 0). I’ve always been puzzled by those who take off a C172 or a C152 with flaps 10º even from a 5000 ft runway.
You have to set full flaps during preflight so that you can properly inspect the hinges etc for the flaps. Unlike the Piper Cherokees the Cessna needs electrical power for flaps up and down.
Running the flap motor on battery is of course possible, but a weak battery may throw in the towel right after you did that when you ask it to now turn over a possibly cold engine with thick oil.
So Cessna decided to leave the flaps in that position and then run the flaps up AFTER engine start when the main drain is gone from the battery and the alternator is turned on.
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The C172P POH doesn’t say anything about waiting to retract the flaps until after engine start. The checklist for the one I fly doesn’t say anything about it either. We always retract the flaps at the end of the walk around, long before the engine is started. But then it also doesn’t get that cold here, so saving the battery to crank the engine in cold weather is less of a concern.
EXACTLY right… 
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Running the flaps up after engine start is what we did in the Aerobat at Art Scholl Aviation, the 172H I flew frequently with a former Lockheed Testpilot and all the 206 and 210 variants used to chase General Dynamics UAVs.
This being SoCal and the HighDesert around KEDW it was not usually that cold.
And I personally always thought leaving the flaps “sticking” out of the wings was a good way to scalp yourself, but the procedure was quite wide spread 
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You lower flaps to have a chance to hit them with your forehead. This is most applicable reason I know 
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I think the same principles also apply in the C152.
Have that t-shirt
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