Extended ground ops/taxiing

[Cardiff Kook]

Is it bad to have engine running on ground for extended period of time?

What if you are taxiing?

I know it’s not great in hot weather as engine air cools, but what about cool/cold?

Curious cause owners handbook says something about limiting ground operations to 2 minutes of ground ops when hot and 4 minutes when cold.

 

[stewartb]

Neither of those time limits is supported by engine monitor temp indications. With your drop light preheat it’ll take longer than 4 minutes to get oil over 70°.

2 minutes is unrealistic for many. Slow taxiing from west Lake Hood to east Lake Spenard comes to mind. I did it for years. Not a problem.

 

[mvivion]

First, one of the concerns with air cooled engines is the possibility of hot spots on cylinders during ground ops. Unless the CHT probes happen to be at one of those hot spots, your CHT instrument may or may not be a reliable gauge during ground ops.

Some of the argument for long ground “warm ups” with horizontally opposed engines may come from procedures developed for radial engines over the years. But, the cylinder cooling problem is very different, at least on a single row radial. On a horizontally opposed engine, development of hot spots on the rear cylinders can be an issue.

As noted in another thread, Lycomings guidance on many of its engines is simply that you can launch when the engine is warm enough to accept full throttle application. That seems like good advice. If you are using oil grade appropriate to temps, that metric should be fine. And, depending on OAT, sitting there at idle MAY wind up being a “cooling off” process, as opposed to a warm up.

Follow your engine manufacturers guidance and you should be good.

MTV

 

[stewartb]

A cowled engine has cooling any time the prop is spinning. The idea that hot spots are a problem is hard to believe and while I’ve looked for science to validate it? I’ve never found any. The best argument against hot spots is in your kitchen. Why do high-end pans use aluminum cores? Because aluminum distributes heat exceptionally well. Not transmits heat, but distributes it.

I’ve ground run my 0-520 for 20 minutes in parking at rpms from 1000-1800. CHTs never reached 300° and oil temp got to about 130° where the thermostatic valve opened, temp dropped slightly, and it never climbed after the oil cooler was flowing.

 

[frequent_flyer]

Curious cause owners handbook says something about limiting ground operations to 2 minutes of ground ops when hot and 4 minutes when cold.

That's funny! DVT had silly long departure delays before COVID greatly reduced flight school activity. I have waited as long as 30 minutes with the poor old O-360 at 1,000 rpm on a lean mixture trying to keep the plugs clean. 3 cylinders have made it to 3,000 hours but one gave up at 2,800 hours.

 

[DENNY]

The main caution with your engine concerning prolonged ground operation would be at higher RPM when doing ski or float operations (long taxi at 2100-2400 RPM). It should not be a issue with RPM 800-1,200 range that you would use for normal wheel taxi. Leaned to the max on ground taxi my cylinders will continue to cool and oil temp drops after flight. As the others have mentioned due to normal flight opps at some airfields it is not uncommon for taxi/hold time to be 10-15 min I have never had a HIGH CHT problem in the 0320 cub or the Cessna both have full CHT/EGT. What you are going to find on most topics is conflicting information with no clear guidance on which takes precedence. This is a perfect example, do you worry about getting oil temp up or keeping cylinder head temp down?? In this case with your plane (every type/engine/location) is different while it is good to CARE about extended ground ops/taxi you should not be CONCERNED as long as you keeps RPMs low. On that note if it looks like I am going to be holding for 15 min in one spot I usually just shut down if my engine is warm. As noted learn to lean properly on the ground to prevent plug fouling, this is also a good time to read up on how to clear a fouled plug, and do a bush runup on gravel/dirt. DENNY

 

[bob turner]

Wiggle your toes, relax, and fly the crap out of that bird.

 

[mvivion]

A cowled engine has cooling any time the prop is spinning. The idea that hot spots are a problem is hard to believe and while I’ve looked for science to validate it? I’ve never found any. The best argument against hot spots is in your kitchen. Why do high-end pans use aluminum cores? Because aluminum distributes heat exceptionally well. Not transmits heat, but distributes it.

I’ve ground run my 0-520 for 20 minutes in parking at rpms from 1000-1800. CHTs never reached 300° and oil temp got to about 130° where the thermostatic valve opened, temp dropped slightly, and it never climbed after the oil cooler was flowing.

Just conveying what I was told at Lycoming's Piston Engine Service School twenty years ago. At idle, that "Pressure Cowl" isn't moving much air.

MTV

 

[mvivion]

Wiggle your toes, relax, and fly the crap out of that bird.

Best advise on this forum.....

MTV

 

[Stankasica]

Might be a problem if you have a pusher.

 

[WhiskeyMike]

2 minutes, 4 minutes. Are they serious? What? On a rocket ship? Curious where this is written down, or how anyone could seriously suggest this based on any real world experience. Note: I'm always willing to be proven wrong. I'm genuinely curious, if a little surprised. I always wiggle my toes while warming up.

 

[Cardiff Kook]

2 minutes, 4 minutes. Are they serious? What? On a rocket ship? Curious where this is written down, or how anyone could seriously suggest this based on any real world experience. Note: I'm always willing to be proven wrong. I'm genuinely curious, if a little surprised. I always wiggle my toes while warming up.

It says it on page 19 of the Piper Owner's Handbook for PA-18-95 and PA-18-135.

2. WARM UP AND GROUND CHECK:
As SOON as the engine starts, the oil pressure should he
checked. If no pressure is indicated within thirty seconds,
stop the engine and determine the trouble.
Warm up the engine at 800 to 1000 R. P. M. for not more
than two minutes in warm weather, four minutes in cold
weather. The magnetos should be checked at 1800 R. P. M.,
the drop not to exceed 1OO R. P. M. The engine is warm
enough for take-off when the throttle can he opened without
engine faltering.

 

[skywagon8a]

Unless your airplane is tied down at the end of the prevailing wind runway, I don't see how it is possible to be taking off in "not more
than two minutes in warm weather, four minutes in cold weather." It usually takes longer than that just to get to the runway.

 

[frequent_flyer]

It says it on page 19 of the Piper Owner's Handbook for PA-18-95 and PA-18-135.


Warm up the engine at 800 to 1000 R. P. M. for not more
than two minutes in warm weather, four minutes in cold
weather.

Perhaps it was intended that 800-1,000 rpm should not be held for more than 4 minutes and that the power should be reduced to idle after that time has elapsed. It may have been good advice when the manual was written but I prefer to keep the rpm above idle to help prevent plug fouling.

 

[frequent_flyer]

Unless your airplane is tied down at the end of the prevailing wind runway, I don't see how it is possible to be taking off in "not more
than two minutes in warm weather, four minutes in cold weather." It usually takes longer than that just to get to the runway.

But that's not what it says. The quoted reference has no mention of time between start and takeoff. It only places a limit on time run between 800 and 1,000 rpm for the purpose of warming the engine.

 

[mvivion]

Perhaps it was intended that 800-1,000 rpm should not be held for more than 4 minutes and that the power should be reduced to idle after that time has elapsed. It may have been good advice when the manual was written but I prefer to keep the rpm above idle to help prevent plug fouling.

Ummm, I think you guys are missing a fairly important evolution.....what comes right after warm up? Taxi. THEN takeoff. I would assume Lycoming is saying that after 2 to 4 minutes of WARM UP, it's time to begin taxiing toward takeoff. Lycoming is very specific in several engines that you should NOT run at more than about 1000 rpm right after start, as in during "warm up". And taxi often involves higher rpm than 1000 rpm.

MTV

 

[frequent_flyer]

Ummm, I think you guys are missing a fairly important evolution.....what comes right after warm up? Taxi. THEN takeoff.

Not for me. I start taxi as soon as possible after engine start. The current version of the Lycoming O/IO-360 operators manual says:

"(4) Warm-up to approximately 1000-1200 RPM. Avoid prolonged idling and do not exceed 2200 RPM on the ground."

I see no advice to perform a warm up before starting to taxi. I see no advice to limit taxi rpm to any specific value. (Maybe there but I didn't find it).

 

[Kodiakmack]

 

[DENNY]

2 minutes, 4 minutes. Are they serious? What? On a rocket ship? Curious where this is written down, or how anyone could seriously suggest this based on any real world experience. Note: I'm always willing to be proven wrong. I'm genuinely curious, if a little surprised. I always wiggle my toes while warming up.

With the cub I am usually in the air within 4-5 min of turning prop . I have a hanger and run multi weight oil. Not really that much in the way of knobs and buttons to push/pull in a cub once the prop turns. Set the altimeter, do rolling run up during 1500 ft taxi and make sure no one is on final, rolling J turn for takeoff and she is off like a homesick angel. Seldom more than 5 min. I don't do hard climb outs, or big pattern and have the engine pulled back before downwind. Once I have been out flying and the engine is warm at sandbar or other strip usually in the air within one min or less. Unless I feel the need to sit and warm the oil/engine say a unheated 20 degree start. I do all that checklist seatbelt, set trim, fuel, and flaps, tapping your head and scratching you butt 3 times stuff before I fire up the engine. Lot less chance of being distracted and having someone walk into the prop or drifting into something.
DENNY

 

[DENNY]

Still snowing so pontification will continue. Why do some pilots do very long warm ups? We have posted a lot of info that would make it possible to do it or not. I would say they do it because that is the way they had been trained. The question then is was it proper training or why was the training done that way. Last week I was talking with a young CFI about how much they made when teaching. He said usually 30-35 dollars an hour which does not sound bad but they would only get paid when the prop was turning. So instructors would have the student start the plane and "warm it up during the 15 -20 min pre-brief. So now all the students think that a 15 min warmup was normal even in a plane that had just flown 20 min before. Remember they will be the new CFI next week. It would be nice to just blame the CFI for this but I would say the blame shared by the flight school for allowing it to happen and the student pilot trying to get by cheap and not pay for the instructors time on the ground which especially after any flight is money well spent. I always paid my instructor for any time he spent with me flying or not. Even paid for his driving time before I soloed and could go pick him up.
DENNY

 

[stewartb]

I don’t move my planes from parking until the CHTs hit 275°. Nobody taught me or told me to do so, I just figured it made sense for the crank and cam to get warm before I applied power. Oil temps need to be >70°, too, and the timing tends to work out pretty well. Plus it gives my mind some time to transition into pilot mode, and that’s more important than the engine temps. Everybody’s situation is different and their reasons for doing things are influenced by it. Nobody’s righter than the next guy.

 

[frequent_flyer]

I don’t move my planes from parking until the CHTs hit 275°.

I don't know what what power it takes to move a max gross Cub with 35 inch tires at 5 psi but the aircraft I own will start to taxi at less then 1,000 rpm when the brakes are released. Why would I stay in one spot when I could move to the run-up point while the engine warms up? The engine really doesn't know, or care, if the airplane has 0 kts GS or 15 kts GS while it warms up.

 

[stewartb]

I don’t taxi very far and I almost always do my run-up while rolling. I don’t spend more than a few seconds at the end of a runway.

 

[WhiskeyMike]

Ummm, I think you guys are missing a fairly important evolution.....what comes right after warm up? Taxi. THEN takeoff. I would assume Lycoming is saying that after 2 to 4 minutes of WARM UP, it's time to begin taxiing toward takeoff. Lycoming is very specific in several engines that you should NOT run at more than about 1000 rpm right after start, as in during "warm up". And taxi often involves higher rpm than 1000 rpm.

MTV

Agreed...What MVivian said. Everything has to be seen in context. Starting up and going wide open before spreading the warmth is a nice way to expand and stress all that metal in a big rush. Aluminum and steel likely expand at direct rates. Beat the daylights out of it if it makes you happy but an engine failure and a forced landing will change your perception in an instant.

 

[Brandsman]

Interesting discussion. I like to see the temps up after start with the C-90 and O-320 at around 90-100 degrees F before doing the run ups and leaning because simply I was always taught never to put full power on a cold engine. I also fly behind a Lycoming GO-480 in a FW Piaggio 149D and that has a Luftwaffe handbook which states that you must idle after starting at 1500 rpm until the oil temperature exceeds 50 degrees C, only then is it permissible to taxi, do run ups, etc. The relatively high “idle” is dictated by the needs of the gearbox not the engine itself - but I would guess that the 50 degrees C (122 F) oil temp is probably a good guideline across the board for engine longevity


Sent from my iPhone using SuperCub.Org

 

[12Geezer2]

So many variables---wind velocity/ direction -airport layout----Remembering a breezy day at Denver Front Range--Ferry flight for a friend---65 H.P. T-cart--wind -out of southwest at 26, gusting 32---it's a LONG taxi to north/south runway---maintaining control was foremost--engine temp. ??? all went well and had nice tailwind all the way to Wi. (GPS said ground speed fairly steady, around 140 and sometimes 147). Fuel stop at Yankton , S.D also very interesting---friendly mechanic propped for me as I tried to hold things together

 

[mvivion]

Let me summarize this discussion: Run your engine as briefly or as long as you like, and choose the appropriate justification from the selections on this thread.

MTV

 

[BC12D-4-85]

Mechanics have told me that oil pressure is as important as temperature before flight. Too cold and/or thick and the viscous oil can create problems....I think added wear from friction or whatever cold oil does when it's forced through close tolerances was implied

Gary

 

[stewartb]

The most meticulous pilots I observe doing engine warmups and cool downs are flying Robinson helicopters with Lycoming engines.