Why the obsession with "complete" run ups 100% of the time

[Liquid_Charlie]

This is mostly directed at float planes but can hold true for other ops such as gravel. Is it a hangover from flight schools and their one rule must fit all and maturity will follow.

My piston flying days we were taught that on floats the only time you did a run up above 1000 RPM was on glassy water basically. Prop damage was just not tolerated and all functions could be checked at 1000 RPM, even props. A mag will run rough at any RPM and then there is the power application, Ramming throttles was also inviting being shit on from a high altitude. Dead mags were checked with mag "burping" and even sometimes a mag shut down of the engine during docking.

On skies sometimes you just could keep the aircraft stationary at high RPM so adapt again.

I watched young guns running up there "hoes" and taking several minutes at high power. It makes no sense to me but I do come from a different era..

[trey kule]

My observations of Navajo run ups, is they tend now to be flown by inexperienced pilots and not really given proper training on type.
Result is flight school training habits sneak into things.
And some mishandling of the engines, because honestly, they don’t know better.

There is still companies that teach 31 ground school by “ reading the POH.
Testing is a joke, and flight training minimal.

[CpnCrunch]

So why does the POH say 1700rpm (or whatever)? There must be a reason.

For float training I was taught to do the runup at 1500/1700rpm with the stick back. I don't see that it could do any more damage to the prop than you're going to do on the takeoff roll.

I can certainly see it being an issue on gravel, but presumably someone has come up with a reasonable solution in the last 70 years. It doesn't really seem like it should be a difficult problem to solve.

[cgzro]

While I agree with most of this post and I most certainly would not run up my little plane on gravel for the same reason, I question the assertion that mags checks at 1000 RPM will always show the same problem at 1700 or more.

The reason is that the mags generate higher voltages at higher RPMs and that higher voltage can cause problems when the capacitor is starting to leak. This is because at the higher voltage the capacitor can ground rather than absorb the spike and this can result in missing. If you get mag problems at higher rpms but not at lower rpms the capacitor is a good place to start. I imagine the same is true in the coil because the paper insulator between the coils if its breaking down could allow shorting between the two coils or the same coil at higher voltages.

I actually had exactly this problem a number of years ago, and rather than just sending the mag off for overhaul I asked my mechanic if we could diagnose the problem ourselves. Since the circuit is dead trivial it was not hard to find the culprit. Anyway I came to the conclusion that you could in a pinch pull the rear cover, swap the capacitor and be flying again in an hour for $25 rather than a full overhaul if you experienced this problem (failure at higher RPM vs lower RMP). In my case my mag had been overhauled only 50 or so hours before but they had clearly not changed the $25 capacitor in spite of the $500+ price that was charged.

[David MacRay]

It’s shocking how desperately reliant on routine some pilots seem to be.

I know, I shouldn’t be picking on them. I probably appear to copy some flight instructors and I do a way more thorough walk around than necessary, but only because I need the practice, in case I ever fly something that is not being checked and flown all day most of the time.

Check lists must be a good thing for a few, it sure looks like someone needs to wipe their noses.

Maybe just add some tips or foot notes like, (Unless on gravel. It could harm the propeller.)

[Liquid_Charlie]

It’s shocking how desperately reliant on routine some pilots seem to be.

I think that is the bottom line. The attitude that it's in the POH it must fit everything 100% of the time is an easy trap to fall into.

Suppressed thinking and dumbing down have been the main driving forces in aviation for several years now. Certainly guidance and teaching tools are required but not at the expense of common sense.

The point I was trying to make is that you can modify the rules and such to fit the situation. That's the difference between a good pilot and a damn great pilot.

[digits]

It’s shocking how desperately reliant on routine some pilots seem to be.

I think that is the bottom line. The attitude that it's in the POH it must fit everything 100% of the time is an easy trap to fall into.

Suppressed thinking and dumbing down have been the main driving forces in aviation for several years now. Certainly guidance and teaching tools are required but not at the expense of common sense.

The point I was trying to make is that you can modify the rules and such to fit the situation. That's the difference between a good pilot and a damn great pilot.

There is seldom a need to break the rules (that's what 'modifying the rules' really means). If breaking the rules becomes your routine, you're likely doing something wrong.

But that's irrelevant for the run up dicussion, there is no rule making a run up mandatory, it's a 'should' thing, no a 'shall' thing.

I noticed you didn't reply to cgzro's post. What's the point of doing a mag check at 1000 rpm?
I've never had a magneto act up at 1000 rpm, but I've had them act up a couple of times above 1600 rpm on smaller pistons, and they were fine at 1000 rpm.

You get to choose between a proper mag check and 15 seconds at medium power with some possible water or gravel damage, or no mag check. If the plane is constantly on floats, I certainly hope you would do a proper mag check at some point...

[Colonel]

Code: Select all

What's the point of doing a mag check at 1000 rpm?

Both times I have had a real magneto failure - one Continental, one Lycoming - both
were obvious at 1000 RPM. There was no need to beat the prop up.

When I start an aircraft, after I check the oil pressure and lean the mixture, in front
of the hangar I check both mags and both brakes. If they both don't work, I shut it down.

Frankly, I'm more concerned about sticking exhaust valves, which often becomes more
apparent at high RPM (and immediately after cold start).

How many people here have taken off running on five cylinders?

[digits]

How many people here have taken off running on five cylinders?

It's surprisingly hard to do with a lycoming O360.

[Colonel]

I am not sure magnetos respect me. Thinking back, over the decades I have seen:

1) magneto switch fail. I know, this isn't really the magneto, but ...

2) p-lead from the switch to the magneto insulation fail, and solid short to ground.
As soon as I diagnosed this - by removing the p-lead from the magneto which started
to work - the owner promptly left, happily flying with a hot mag. Sigh.

3) coil fails in the magneto. This was one of my Continental / Bendix magneto failures.
IFR flight to Ottawa. Stopped for gas. Checked mags after start - one was dead. See
the coil AD.

4) condensor fail in the magneto. Above 150F, the points would start to arc. Try
diagnosing that one without an engine monitor. Condensor (actually .28uF capacitor)
had a grand total of 90 hours in service, but a few years which was probably the problem.

5) rotor cap wore and started to wobble and burn rotor tip and individual pickups.
Again, tough without an engine monitor.

6) spark plug resistance increased and started arcing inside the magneto - less
resistance, I guess. A lot like #5 above.

7) external capacitor (noise suppressor) strapped onto magneto failed and gave
me a lot of radio noise on certain frequencies. This one can be hard to diagnose.

Amazingly, I have never seen points fail in a magneto, thinking about it, which is
pretty weird. They need to be gapped properly, and they burn when the condensor
fails.

Anyways, I have never learned much more about magnetos at 1700 RPM than
1000 RPM. I am much more interested in a buzz up to 2400 RPM to check for
valve float (lead deposits), but you need a perfect paved surface for that, and
generally the aircraft will start moving even with full brakes. Reminds me of the
guys running up -104's, having to chain them down.

PS I shouldn't post this, but this is what the Pitts S-2B POH says: