Runup on Snow

[chrisk]

The recent winter weather has me pondering procedures for a run up when the runway/taxiway is slick with snow.    Maybe 2 inches before the plow has made it to the runway.  Its been many years since I've had to do this, and as I recall the brakes would not hold on a snow covered taxiway/runway.  I think we gave it our best shot while moving on the taxi way (or runway), but the details have faded.     For those that deal with snow covered airfields on a regular basis, what is your run up procedure?   

[gsengle]

I fly for Cape Air out of the Adirondacks in addition to having a Mooney. This mornings ramp photo below. No good answer. Don’t do it at the hold short line. Do it on a taxiway with lots of room particularly ahead. Keep it quick. A run up needn’t take 10 mins like it seems some GA pilots take. Be prepared and run your flow or checklist. Not all of the pre takeoff stuff is high rpm. It can be done while moving in a pinch but it’s not the safest. In a twin it’s worse due to asymmetric thrust while exercising props, so it’s not recommended...

Preheat so you don’t need a long warm up.

[aviatoreb]

19 minutes ago, gsengle said:

I fly for Cape Air out of the Adirondacks in addition to having a Mooney. This mornings ramp photo below. No good answer. Don’t do it at the hold short line. Do it on a taxiway with lots of room particularly ahead. Keep it quick. A run up needn’t take 10 mins like it seems some GA pilots take. Be prepared and run your flow or checklist. Not all of the pre takeoff stuff is high rpm. It can be done while moving in a pinch but it’s not the safest. In a twin it’s worse due to asymmetric thrust while exercising props, so it’s not recommended...

Preheat so you don’t need a long warm up.

No kidding - you fly for Cape Air out of KSLK?!  I'm based at KPTD and I've been many many times to KSLK - mostly for the diner.

This morning was cooooold eh?

E

[gsengle]

Tonight was worse, when I had to turn around back to BOS!

ps, during a snow run up keep your head up enough to see if you start to slide...




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[Marauder]

Flew for years in Buffalo. Like it was pointed out, there is no easy way to do a run up. At airports with long taxiways, I would increase the power enough to cycle the prop. And I would count on the engine analyzer to see if all the plugs were firing and mixture was providing an increase - even at lower RPMs.

If I couldn’t get a full power run up, I would watch the engine analyzer as the power was increased - and hope if the runway was icy too that I could stop if I had to.


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[aviatoreb]

21 minutes ago, gsengle said:

Tonight was worse, when I had to turn around back to BOS!

ps, during a snow run up keep your head up enough to see if you start to slide...




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That stuff you are on there isn't even the worst - that's cold snow/powder which has some traction to it almost like sand sometimes.  But sometimes it can be quite slick at the hold short point with really slick ice.  Point well made to consider the surface we do our run up on.  Often some parts of the tarmac will be better than others and maybe to do the run up where traction is best.

[N201MKTurbo]

1 hour ago, gsengle said:

I fly for Cape Air out of the Adirondacks in addition to having a Mooney. This mornings ramp photo below. No good answer. Don’t do it at the hold short line. Do it on a taxiway with lots of room particularly ahead. Keep it quick. A run up needn’t take 10 mins like it seems some GA pilots take. Be prepared and run your flow or checklist. Not all of the pre takeoff stuff is high rpm. It can be done while moving in a pinch but it’s not the safest. In a twin it’s worse due to asymmetric thrust while exercising props, so it’s not recommended...

Preheat so you don’t need a long warm up.

Does Lowell still work there?

[Shadrach]

On 1/19/2019 at 7:43 PM, chrisk said:

The recent winter weather has me pondering procedures for a run up when the runway/taxiway is slick with snow.    Maybe 2 inches before the plow has made it to the runway.  Its been many years since I've had to do this, and as I recall the brakes would not hold on a snow covered taxiway/runway.  I think we gave it our best shot while moving on the taxi way (or runway), but the details have faded.     For those that deal with snow covered airfields on a regular basis, what is your run up procedure?   

What’s your goal with the run up? What are you really learning?

 I stopped doing stationary 1700 rpm run ups a few years after getting an engine monitor. I verify prop/mixture/throttle control continuity and insure that both mags are operating, but that’s doable during taxi. I do an inflight, high power, LOP mag check on almost all flights. I have tried to come up with a logical reason to do a brakes locked 1700rpm (or whatever subjective rpm one wants to use) run up. I’ve been unable to make a compelling argument that it has much utility.

Edited January 22, 2019 by Shadrach

[gsengle]

What’s your goal with the run up? What are you really learning?
 I stopped doing stationary 1700 rpm run ups a few years after getting an engine monitor. I verify prop/mixture/throttle control continuity and insure that both mags are operating, but that’s doable during taxi. I do an inflight, high power, LOP mag check on almost all flights. I have tried to come up with a logical reason to do a bakes lockexked # (or whatever subjective rpm one wants to use), I’ve been unable to make a compelling argument that it has much utility.

You need to exercise the prop and ensure warm oil is in the hub. This requires high rpm. This is 3x more critical in a twin tho, where you need to make sure you can feather. Mag check can’t be deferred to flight either. The first 1000 feet of climb is the biggest danger.... Also you need to get the engine fully warmed up, which takes power in the winter. Finally a run up stresses the engine which could expose any problems before the roll, and can clear fouled plugs.


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[Guitarmaster]

16 hours ago, gsengle said:

You need to exercise the prop and ensure warm oil is in the hub. This requires high rpm. This is 3x more critical in a twin tho, where you need to make sure you can feather. Mag check can’t be deferred to flight either. The first 1000 feet of climb is the biggest danger.... Also you need to get the engine fully warmed up, which takes power in the winter. Finally a run up stresses the engine which could expose any problems before the roll, and can clear fouled plugs.


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I will have to disagree...

The oil in the hub never gets warm. I didn't know this till I flew three hours to @Cody Stallings shop to have the prop resealed. Pulled the prop and freezing oil came out. Prior to that, I was always told I needed to cycle the prop to get the oil flowing. I learned all kinds of prop things on that trip.
The only check on a twin is the feather check which is performed at 1000RPM, at least in my 310.
I do two mag checks. One on the ground at around 1200 and one inflight. If it's rough at low RPM or I don't like what I see on the monitor, then I run it up. The inflight check is a much better ignition stress test.

As far as snow, do what's safe. High-power run-ups on slippery taxiways really are not a good combo. Your head is down and the airplane really wants take off.

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Edited January 20, 2019 by Guitarmaster

[gsengle]

I will have to disagree...

The oil in the hub never gets warm. I didn't know this till I flew three hours to @Codystallings shop to have the prop resealed. Pulled the prop and freezing oil came out. Prior to that, I was always told I needed to cycle the prop to get the oil flowing. I learned all kinds of prop things on that trip.
The only check on a twin is the feather check which is performed at 1000RPM, at least in my 310.
I do two mag checks. One on the ground at around 1200 and one inflight. If it's rough at low RPM or I don't like what I see on the monitor, then I run it up. The inflight check is a much better ignition stress test.

As far as snow, do what's safe. High-power run-ups on slippery taxiways really are not a good combo. Your head is down and the airplane really wants take off.

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Watch the oil temp gauge when you cycle the prop in cold weather. You have to confirm that it can flow, more than it is to warm it up per se, fresh oil moving. You’ll see the temp drop. I’m surprised that the feather check is so low, most prop hubs you don’t want to actuate to below 1000 rpm, the check is more like 1700 rpm


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[Guest]

11 hours ago, chrisk said:

The recent winter weather has me pondering procedures for a run up when the runway/taxiway is slick with snow.    Maybe 2 inches before the plow has made it to the runway.  Its been many years since I've had to do this, and as I recall the brakes would not hold on a snow covered taxiway/runway.  I think we gave it our best shot while moving on the taxi way (or runway), but the details have faded.     For those that deal with snow covered airfields on a regular basis, what is your run up procedure?   

If you have enough ramp space, bring the plane to a stop and bring the power up a bit.  The prop blast will clear away much of the snow under the prop and engine area, reduce the power and taxi in a circle ending up on the area you just cleared.  In many cases you now have a clear spot to do your full run up.

For those who advocate for a pre flight run up not following the PoH, if you have an accident and the FAA or your insurance company downloads your engine monitor,  are you not opening to possible enforcement action or claim denial?

Clarence

Edited January 20, 2019 by M20Doc

[gsxrpilot]

What would the consequences be of taking off and the prob oil wouldn't flow? I believe the prop would stay at full fine pitch and you would not be able to reduce RPM. Correct? 

[Andy95W]

13 hours ago, gsengle said:

 

. I’m surprised that the feather check is so low, most prop hubs you don’t want to actuate to below 1000 rpm, the check is more like 1700 rpm
 

 

It is normal for a multi-engine aircraft.  On our airplanes, we check that the prop will go to coarse pitch, which means you have to be in the governing range (or above 1700, like you said).

On multi-engine airplanes, you also have to check that the prop goes into feather, which means you must not be in the governing range, or some rpm well below 1700.

[carusoam]

In most Mooneys....

• if the Governor’s gear pump isn’t supplying oil pressure
• or the control valve is stuck open
• or the seal at the end of the shaft has fallen out

The low oil pressure situation occurs to the prop blade angle controller... the blades will sit on the high rpm stops...

The high rpm stops are not at 2700rpm, they are a bit higher....

The other Mooneys are Missiles and Rockets with their twin related props that fail in the feathered position... great for gliding, terrible during T/O...

So... make sure the rpm control is functioning prior to T/O...

If the shaft seal has gone on vacation... the result is an over speed while making full power.  To come off the overspeed requires pulling the MP back... more than a comfortable amount....

It becomes like flying a fixed pitch prop, but With the wrong blade angle....

Being familiar with the engine manufacturer’s definition of overspeed... how many rpms for how long is acceptable can be helpful....

my 65C’s shaft seal went on vacation one day... putting it back requires removal of the prop... after checking all the other things related to the Governor...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Shadrach]

Oil doesn’t flow through our hubs. Run ups are not a limitation and they are not regulatory. The POH also tells me to pull back to 25 inches for climb, I don’t do that either.  As I said before, I don’t do a standard high rpm run up because it doesn't  give me any more information then I’ve already gleaned from a control continuity check and observing my engine monitor.  I’m not breaking a single FAR, I’ve merely stopped doing a procedure that was recommended long before engine monitors. Procedures evolve for a reason. 

Edited January 24, 2019 by Shadrach

[gsengle]

Well doesn’t flow through our hubs. Run ups are not a limitation and they are not regulatory. The POH also tells me to pull back to 25 inches for climb, I don’t do that either.  As I said before, I don’t do a standard high rpm run up because it doesn’t  give me any more information then I’ve already gleaned from a control continuity check and obseving my engine monitor.  I’m breaking a single FAR, I’ve merely stopped doing a procedure that was recommended long before engine monitors. Procedures evolve for a reason. 

A brand new Mooney or Cirrus have both engine monitors and run-ups. You can’t know all the reasons these tests are in the AFM/POH. Ignorance of doesn’t prove non existence of.


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[Shadrach]

5 hours ago, gsengle said:

 

A brand new Mooney or Cirrus have both engine monitors and run-ups. You can’t know all the reasons these tests are in the AFM/POH. Ignorance of doesn’t prove non existence of.


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 What I can know is that my prop is 8 inches off the ground and that sucking stones into it for no good reason doesn’t add to my safety. Given that you fly for a living, I fully understand the environment you operate in. It’s important to have standard procedures, it’s important to have them in writing, and it’s important to follow them.

I however, don’t operate in that environment. You may not think that I can know all the the reasons for a run up  and you may be right (but probably not). I’ve had three ignition failures in the last 15 years. Two of them were mag related, one with spark plug related. Run ups caught exactly 0% of them.  Once one really gets accustomed operating according to monitor feedback over what I would call cookbook operations, one begins to eliminate practices that don’t yield much return (if any) in information.  

I’m not telling anybody not to do a run up, my comments posed the question “what are you getting out of your run up?”.

 In your case, you thought you were circulating fresh, warm oil to the prop. You may be in some of the airplane’s you fly, but not in a Lyc powered Mooney. 

Cycling the prop in any factory Mooney is like a front end loader operator raising and lowering his bucket, it doesn’t circulate fresh hydraulic fluid to the bucket’s piston.

Edited January 21, 2019 by Shadrach

[gsxrpilot]

I'm with Ross on this one. Get an engine monitor and know how to read it. Fly one airplane and fly it regularly (every few days). Know your airplane. 

[gsengle]

I'm with Ross on this one. Get an engine monitor and know how to read it. Fly one airplane and fly it regularly (every few days). Know your airplane. 

No one is against any of that lol


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[Shadrach]

6 hours ago, Andy95W said:

It is normal for a multi-engine aircraft.  On our airplanes, we check that the prop will go to coarse pitch, which means you have to be in the governing range (or above 1700, like you said).

On multi-engine airplanes, you also have to check that the prop goes into feather, which means you must not be in the governing range, or some rpm well below 1700.

Your prop will go course at 900rpm. Check it out if you don’t believe me. 

[squeaky.stow]

I think the original question was how do you do a runup on slippery taxiways.

As someone who flies regularly from snow covered airports, the answer is really just try it and see what happens. I will always look for some bare pavement, but sometimes there is nothing to be found. You will have a pretty good idea just how slippery it is long before you get to the runup area. Snow over pavement is usually not that bad. Snow over ice is much worse, and wet ice is bad enough that you will be sliding around at idle power, so do a braking check as soon as you start moving and be ready to go to cut-off on the mixture if you can’t stop.

That being said, it is pretty rare that 1700 rpm will cause me to start sliding around unless the surface is ice covered. If I am sliding around so much that I can’t safely do a runup anywhere, I am not sure I want to go flying, especially if there are good crosswinds. That's the nice part about flying my Mooney. I don’t ever HAVE to go flying.

Regards,

Mark

[Guest]

42 minutes ago, Shadrach said:

 

 In your case, you thought you were circulating fresh, warm oil to the prop. You may be in some of the airplane’s you fly, but not in a Lyc powered Mooney. 

Cycling the prop in any factory Mooney is like a front end loader raising and lowering his bucket, it doesn’t circulate fresh hydraulic fluid to the piston.

Now I’m confused.  Oil under pressure from the governor causes blade pitch change in constant speed propellers.  

In our case when we pull the prop control toward coarse, the governor high pressure oil displaces the piston in the prop causing the blades to coarsen. When we move the prop control toward fine we drop governor oil pressure, springs within the prop as well as aerodynamic twisting moment of the blades move the blades toward finer pitch angle.  

If the piston is being displaced,  oil is entering and exiting to prop via the governor, so oil of what ever temperature (presumably warmer than the propeller oil) in the engine is mixing with oil in the propeller piston and dome.

Clarence

[gsengle]

Now I’m confused.  Oil under pressure from the governor causes blade pitch change in constant speed propellers.  
In our case when we pull the prop control toward coarse, the governor high pressure oil displaces the piston in the prop causing the blades to coarsen. When we move the prop control toward fine we drop governor oil pressure, springs within the prop as well as aerodynamic twisting moment of the blades move the blades toward finer pitch angle.  
If the piston is being displaced,  oil is entering and exiting to prop via the governor, so oil of what ever temperature (presumably warmer than the propeller oil) in the engine is mixing with oil in the propeller piston and dome.
Clarence

On a cold day first run up of the day you can watch your engine oil temp gauge drop dramatically as you move oil in and out of the cold prop during run-up. Of course you’re getting warmer less viscous oil in there. QED


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[ArtVandelay]

Maybe the oil isn’t circulating, but there is oil going in and out of the hub.


Tom