Turning into the wind for runup

[flyingcheesehead]

I like Deakin, but in this case (and how many others, I wonder?) he's offering opinion, not fact.

Nope... They were using a primitive measuring system. My recollection matches that of @Checkout_my_Six:

According to the wise folks at APS....it has to do with "reverse" flow out the cowling around the prop hub....and some measured theory using video and tufts.

They claim that a "tail wind" is better for improved engine airflow than facing into the wind. The prop acts like a disk and the flow is directed off the disk into the engine....Could be....but I doubt it makes that much of a difference....cept when arguing over the topic on an internet forum.

 

[aftCG]

Damn you fellas are arguing about something that would be so easy to test in any airplane with CHT and a breeze. Are we taking bets? I bet OWT.

Nothing OWT about it. I fly radial engine planes specifically placarded to perform run ups into the wind.
And as others have pointed out it is more about the time spent idling while performing the non-runup tasks on the checklist.

A dive into the (book that serves as the) AFM it tells you to complete the run up portion in less than 30 seconds.

It's not that there's no air flow, it's that it is very uneven. The aft side of the cylinders are all sitting next to a cooking hot exhaust manifold (post mag and prop check) while the fronts are getting a slight cool breeze. Bad.

On occasions when my location in the conga line prevents air flow consideration I find that I can smell it getting hot before the CHT registers it (CHT is single probe on these old geezers so you aren't getting a complete story, so the sensor on the front of your head comes in handy).

That’s my challenge in the Waco. Takes FOREVER to get the oil up to temp. If it’s cool out, I basically point away from the wind while waiting for the oil to warm up and then point into the wind for the actual run up.

Been there many times. With the R985 and R1340 I run them at 1000rpm with the carb heat on and the oil cooler shutters closed. The latter probably isn't doing anything but carb heat definitely speeds things up.

As I figure it, 15 minutes spent listening to a radial is not time wasted in this life.

As for consideration of others during run up, well let's just say it is part of training but there are a lot of a**holes in this world.

A few years so I felt like one of them. Tons of people leaving the Arlington air show and I got blocked in line with my tail pointed at the row of RVs. One of my GoPro cameras caught the sight of picnic awnings taking a beating and debris flying. In the middle sat this old dude in a chair, hair blowing back and smiling.

 

[jordane93]

Except for those looking to get 90 day current before reaching the runway.

Best I did for night currency 0.3! Rolling run up, short approach/power off 180, shut down engine pulling into parking spot lol.

 

[Stewartb]

I've had occasion to ground run my Cessna for 20 minutes in parking at 1500_1800 rpm. CHTs peaked at under 300*. Guys give way too much concern to ground CHTs. Even in a 10mph downwind the prop is pressurizing the cowl, too. Go stand behind a plane and find out for yourself. 30-40 mph? It matters.

 

[kyleb]

Nope... They were using a primitive measuring system. My recollection matches that of @Checkout_my_Six:

According to that theory, an airplane would cool better flying backwards than forwards. My experience contradicts this.

 

[Checkout_my_Six]

I've had occasion to ground run my Cessna for 20 minutes in parking at 1500_1800 rpm. CHTs peaked at under 300*. Guys give way too much concern to ground CHTs. Even in a 10mph downwind the prop is pressurizing the cowl, too. Go stand behind a plane and find out for yourself. 30-40 mph? It matters.

ya but....the root of the prop doesn't move as much air as the tips.

 

[LongRoadBob]

I’ve read some places, use it when there is wind to be had, because the engine is made up of different materials that heat up at different rates you want to heat up as slowly as possible so the heat is even among parts.

Also was thinking the propeller near the spinner is not traveling as far so much less wind into the engine.

Our school only charges (+5 minutes each side) from just before takeoff so our run up checklist is not generating any extra income. I think it takes about five minutes or so.

We are taught to do it into wind if there is wind, before we taxi on to the runway.

one thing I don’t understand, our checklist never mentions leaning the engine after run up. We have checklists in order pre-startup, startup, warm up, taxi, run up. Then before takeoff. In the startup, after checking oil pressure, instructs is to lean the motor.
But after run up no mention of leaning. The POH says clearly for ALL ground operations one should lean. So I assumed we lean after run up until before takeoff. There is a check that miscue is full on in the before takeoff checklist. My instructor said “no, it’s not in the checklist” and he’s a very experienced pilot and instructor.
I don’t get it. If the wind is coming from SE specially we have a decent distance to taxi.

 

[MauleSkinner]

one thing I don’t understand, our checklist never mentions leaning the engine after run up. We have checklists in order pre-startup, startup, warm up, taxi, run up. Then before takeoff. In the startup, after checking oil pressure, instructs is to lean the motor.
But after run up no mention of leaning. The POH says clearly for ALL ground operations one should lean. So I assumed we lean after run up until before takeoff. There is a check that miscue is full on in the before takeoff checklist. My instructor said “no, it’s not in the checklist” and he’s a very experienced pilot and instructor.
I don’t get it.

Your instructor, however experienced he is, apparently doesn’t understand “airmanship”, which includes being familiar with and following the guidance in the POH.

The checklist doesn’t tell you a lot of things. It’s merely intended to ensure that the important items aren’t forgotten. If they put everything in he checklist that’s in the POH, it would be, um, a POH.

 

[Palmpilot]

In 28 years of flying, I have yet to find a perfect checklist.

 

[flyingcheesehead]

According to that theory, an airplane would cool better flying backwards than forwards. My experience contradicts this.

No - In flight, there's going to be a ton of ram air coming in the front of the cowling. When at rest on the ground, there isn't any except for what the prop puts in there or whatever headwind you have. I can see the prop reversing a tailwind into the cowling.

 

[bluerooster]

Wouldn't the air flow from the prop overpower any kind of tailwind there might be?

Very little wind from the prop that close to center line.

 

[mryan75]

Why is it recommended that we turn into the wind when doing our run up?

I asked an old instructor, he said it's pointless. How long do you do your runup? If it's long enough to overheat your engine, you might be doing something wrong.