Some more thoughts on training.

[Chuck Ellsworth]

Thanks for the comments slick, they are exactly what we need here to come up with ideas on where flight training can be improved.





[quote]
It's often a lowest-common-denominator thing (unless recommended or demanded by the POH) and like SOP creep this stuff appears to just get dumber as time goes on.  I have some thoughts on fixing it, but they wouldn't go over well.[/quote]


That is why I started this subject, to find out why pilots do certain things that can be counterproductive to good airplane handling procedures.


When taxiing and you want to reduce taxi speed the first thing to do is reduce power....far to many are taught to use brakes and leave the power as set.


For the sake of this discussion we will stich with the common training airplanes and their engines....little Continentals and Lycomings.

If we identify where improvements can be made the next goal is to discuss how there improvements can be made.

[Trey Kule]

Interesting topic. some of the posts as well.

First of all, with regard to taxiing.  I too, have witnessed  those that taxi an aircraft like they just stole it. More than a  few Cessna twins with rippled belly skin from fast cornering.

Perhaps we could discuss with students how to manage energy.  Push the gas pedal on you car..Car moves, gets near the speed, back off the gas a bit...Almost without thinking after awhile.

Now a plane.  Push the throttle it, and the little rascal starts to move.  That is the time we should be reducing the throttle, as the aircraft  will continue to accelerate, and one has to manual reduce the throttle, not just release it..  If you are already taxiing to fast, the student is behind in energy management.
This, BTW, is not a ppl student issue.  An issue even for some CPL licensed pilots.
do instructors discuss this with students about reducing power before they get to taxi speed?  or teach them how to deal with it after they have already gotten to fast?  Pretty simple thing to get across to students if we try.
(as an aside, the energy management issue is also a good discussion in attitudes and movements to understand why not to chase the airspeed)

Now the RPM thing.  Interesting.  No one in their right mind would start a cold radial and immediately bring it up to 1000 rpm.
They are dry sumped and get lots of oil at low rpms (generally speaking).  Now the horizontal opposed little rascals like to pick up some oil from the crankshaft.  And so, like to get to those higher numbers.
The challange is, taxiing, overheating on hot days, and oil management.  Maybe plug founding, though I do not ever personally recall that being a problem.
These do not all fall in line with the 800-1000 rpm range, which results in fast taxi, riding brakes, overheating on the ground.
Or taxiing with a bit lower RPM.
One has to learn the specific machine a bit ,I suppose, to get it all as best matched as possible.

Rather than argue about it, I think the thing here is if you are flying behind these engines, get some real advice...as in the websites of the manufacturer, using their contact to ask a technician  I am not convinced that an internet forum may be the best place, and to make the point, I am taking all the foregoing from memory.

[JW Scud]

I have encountered the rpm versus braking issue on light aircraft as well. Ideally, I would like to taxi out at a reasonable speed with minimal brake applications. But frequently, that requires keeping the rpm at or near idle which from what I have been told, leads to fouled plugs even with the mixture leaned(I believe). It is a bit of a damned if you do and damned if you don't situation.

Recently, I have been trying to do a combination of both keeping a decent rpm, hopefully as close to 1000 rpm as possible with engine leaned but hopefully low enough to minimize brake applications. Taking note of the slope of the taxiway you are on can be helpful for engine/taxi speed management on occasion.

One aircraft I fly has a recommendation of 1100 rpm as a minimum. Another flight school was recommending full rich operations during ground ops until they changed their policy recently.

I would be interested to hear what others are doing. Are you just maintaining a higher rpm and doing lots of brake applications, or a low rpm and not worrying about plug fouling issues?

[Chuck Ellsworth]

[quote]I have encountered the rpm versus braking issue on light aircraft as well. Ideally, I would like to taxi out at a reasonable speed with minimal brake applications. But frequently, that requires keeping the rpm at or near idle which from what I have been told, leads to fouled plugs even with the mixture leaned(I believe). It is a bit of a damned if you do and damned if you don't situation. [/quote]


I can only speak from my own experience with training aircraft based on having owned a fleet of light aircraft and also my own AMO.


In all the decades of flying and maintaining them I do not recall any significant issues with lead fouling of plugs.


And all my instructors were taught if the airplane is going to fast during taxi first close the throttle, then use brake if really needed.


As I have said on many occasions there is no way you can safely taxi and dock a float plane unless you use minimum RPM including going to only one mag at times to get it turning slower.

[JW Scud]

[quote author=Chuck Ellsworth link=topic=5879.msg15481#msg15481 date=1490060775]
[quote]I have encountered the rpm versus braking issue on light aircraft as well. Ideally, I would like to taxi out at a reasonable speed with minimal brake applications. But frequently, that requires keeping the rpm at or near idle which from what I have been told, leads to fouled plugs even with the mixture leaned(I believe). It is a bit of a damned if you do and damned if you don't situation. [/quote]


I can only speak from my own experience with training aircraft based on having owned a fleet of light aircraft and also my own AMO.


In all the decades of flying and maintaining them I do not recall any significant issues with lead fouling of plugs.


And all my instructors were taught if the airplane is going to fast during taxi first close the throttle, then use brake if really needed.


As I have said on many occasions there is no way you can safely taxi and dock a float plane unless you use minimum RPM including going to only one mag at times to get it turning slower.
[/quote]

Thanks,

Obviously docking is an area where there is an overriding safety factor. But this is an extremely short amount of time compared to the thousands of hours of taxiing on paved airports around the country. So after taking into consideration, your important point, what about the typical taxiing situation on a paved taxiway.

I notice that you mentioned that you never had an issue with fouled plugs and that you had earlier mentioned about having operated Grumman Cheetahs at a flight school. Did you primarily use 80 octane, 100 octane, or 100 LL?

[Rookie Pilot]

Fouled plugs happen in my experience from way , way too much time at full rich.


Start, lean, leave mixture alone until takeoff. Including run up.


Takeoff, level cruise power, lean. Note I used 65-70% most of the time.


Descend, leave lean. Richen very  slightly if descending from 9000', a couple of times.  Downwind, base, leave lean. Turn final, full Rich. Engine has cooled by then.


Exit runway, back to lean.


0-540, plugs stayed clean.

[Chuck Ellsworth]

[quote]Obviously docking is an area where there is an overriding safety factor. But this is an extremely short amount of time compared to the thousands of hours of taxiing on paved airports around the country.
[/quote]


Taxing on floats very often requires most of the taxi to be at low RPM.


And as I have stated during the thousands of hours my training aircraft were taxied I made sure the taxi speed was controlled first by power then use brakes if really needed.



[quote]So after taking into consideration, your important point, what about the typical taxiing situation on a paved taxiway.[/quote]


Read above comments


[quote]

I notice that you mentioned that you never had an issue with fouled plugs and that you had earlier mentioned about having operated Grumman Cheetahs at a flight school. Did you primarily use 80 octane, 100 octane, or 100 LL?[/quote]


We used all of the above....and plug fowling was never a significant concern ever..


Plug fowling will show up during the runup as long as the instructors understand the subject....it can be burnt off by leaning usually, if the problem persists they wrote it up and I fixed the problem.

[JW Scud]

[quote author=Chuck Ellsworth link=topic=5879.msg15484#msg15484 date=1490062254]
[quote]Obviously docking is an area where there is an overriding safety factor. But this is an extremely short amount of time compared to the thousands of hours of taxiing on paved airports around the country.
[/quote]

Taxing on floats very often requires most of the taxi to be at low RPM.

And as I have stated during the thousands of hours my training aircraft were taxied I made sure the taxi speed was controlled first by power then use brakes if really needed.

[quote]So after taking into consideration, your important point, what about the typical taxiing situation on a paved taxiway.[/quote]

Read above comments
[quote]

I notice that you mentioned that you never had an issue with fouled plugs and that you had earlier mentioned about having operated Grumman Cheetahs at a flight school. Did you primarily use 80 octane, 100 octane, or 100 LL?[/quote]

We used all of the above....and plug fowling was never a significant concern ever..
Plug fowling will show up during the runup as long as the instructors understand the subject....it can be burnt off by leaning usually, if the problem persists they wrote it up and I fixed the problem.
[/quote]

Thanks for the opinions. For myself, I will continue to at least attempt to comply with recommendations by the engine manufacturers. The link below to Lycoming provides recommendations for engine operation. Their recommendation is at 1000-1200 rpm. Obviously if a more important reason to operate differently occurs(which will likely only be on a temporary basis), that will be done.


https://www.lycoming.com/sites/default/ ... ouling.pdf


"Avoid prolonged closed throttle idle engine speed operation (when possible). At engine speeds from 1000 to 1200 RPM, the spark plug core temperatures are hot enough to activate the lead scavenging agents contained in the fuel which retards the formation of the lead salt deposits on the spark plugs and exhaust valve stems."

[red_shiny_ribbon]

Shhhhh, Chuck knows better than the engine manufacturer. He has thousands of hours teaching others.