RPM Surge when pulling the mixture too much

[A64Pilot]

2 hours ago, Pinecone said:

Most of the development of the LOP movement in GA was done with NA and turbo normallized engines.

The original work was with supercharged and turbo supercharged big radials.

It’s actually been done nearly forever, just it wasn’t marketed if you will and given a name of LOP, that’s because until recently recently there was no EGT measuring device, you went by “feel” or RPM. The old guys at night would watch the color of the exhaust flames to set mixture. But nearly everyone who had an engine capable of LOP has run it that way for a very long time. 

The P-38 had electric props, so the governor could be turned off with a switch, the procedure for extended range cruise was to set MP and prop at cruise settings, then turn off prop governor then slowly lean it until I think you got a 50 RPM drop, then leaving it lean turn back on the prop governor, repeat for second engine.

Most everyone else leaned until it got rough then slowly enriched just enough to smooth it out.

Radials are good for mixture evenness as every cylinder is exactly the same, same induction tube etc. and of course both the P-38 way with its inline engine and the add mixture just until it smooths out in a radial put them both LOP.

The little flat carbureted motors that wouldn’t run LOP came later or at least didn’t become the standard GA engine until after WWII

[Shadrach]

11 minutes ago, A64Pilot said:

Notice how much quicker she went to the left and how much difference in pitch was required.

It rolls of course better going with engine torque than against it. But be careful if anyone tries this, on a slick airplane like a Mooney airspeed can easily get out of control if you let the nose drop too much.

I’ve got neighbors that will teach you aerobatics in a Zlin if anyone had the itch, better than trying it yourself in a Mooney.

I’m old and don’t have the stomach for it anymore myself

I enjoy positive G aerobatics in appropriately rated aircraft. The rolls in the video were suboptimal (especially the second) to put it nicely. He either pulled too hard at the 180° mark or didn’t adequately pitch up st the start of the roll. He rolled out nose low and was likely accelerating rapidly when he began to arrest the descent.

Posting a video of yourself doing something illegal is bad. Posting a video of yourself doing something illegal and at a minimum level of skill is worse.

It is a slick airframe for sure which makes it unforgiving.  All the more reason for someone with minimum skills not to roll a Mooney much less film it. 

Performing aerobatics in a standard category aircraft is sort of like the tasteless “riding a moped” joke. It might be fun while doing it but you don’t want anyone to see you.

[Shadrach]

12 hours ago, Fly Boomer said:

Yikes!  No thank you.

Let me change my original statement to “There are some perfectly safe things I might do solo, that I wouldn’t want to risk giving a passenger a bad experience.”  Could be as simple as rate of descent.  I can probably tolerate a faster descent than some passengers.  First time I flew with my Mother, I was doing great until she made the first turn.  I was not okay with the bank.  I might tighten my belt and bounce along in some light chop but, in deference to a passenger, I would try to get out of the bumps.

Being hyper vigilant about passenger comfort came late to me. I learned to fly in my early twenties and the flying culture within the young instructor community was not the best in the late 90s.
Flying flapless tail draggers made me better at drag and energy management, but I realized that I had started horseing my F model around in the pattern like a Decathlon. The airframe handles it just fine but passengers not so much. 

[A64Pilot]

11 minutes ago, Shadrach said:

I enjoy positive G aerobatics in appropriately rated aircraft. The rolls in the video were suboptimal (especially the second) to put it nicely. He either pulled too hard at the 180° mark or didn’t adequately pitch up st the start of the roll. He rolled out nose low and was likely accelerating rapidly when he began to arrest the descent.

Posting a video of yourself doing something illegal is bad. Posting a video of yourself doing something illegal and at a minimum level of skill is worse.

It is a slick airframe for sure which makes it unforgiving.  All the more reason for someone with minimum skills not to roll a Mooney much less film it. 

Performing aerobatics in a standard category aircraft is sort of like the tasteless “riding a moped” joke. It might be fun while doing it but you don’t want anyone to see you.

I’m not abdicating it, that’s why the warning of speed and mentioning I have neighbors that will teach you in a Zlin.

Other than rotary wing I’ve not really played with aerobatics, honestly don’t have the stomach. I can tolerate it much better if I’m flying, but my tolerance is about two maneuvers then I have a mouth full of puke, and that’s just not fun.

I got my fixed wing instrument / Commercial in a Part 141 school, that of course was meant to train up and coming Airline drivers, as such we were taught that the stall and gear horn etc should never sound and to make prop RPM adjustments smoothly etc. so as not to upset the folks in back.

So I got that from the beginning, but of course flying a Crop Duster is different. I didn’t spray for money but still did some work.

[Shadrach]

1 minute ago, A64Pilot said:

I’m not abdicating it, that’s why the warning of speed and mentioning I have neighbors that will teach you in a Zlin.

Other than rotary wing I’ve not really played with aerobatics, honestly don’t have the stomach. I can tolerate it much better if I’m flying, but my tolerance is about two maneuvers then I have a mouth full of puke, and that’s just not fun.

I went to an airshow last summer where there was an Edge 540 putting on a routine that made me want to puke just watching. It wasn’t graceful and it wasn’t pretty to watch. The most impressive thing about it was that the pilot was able to maintain consciousness and not shower the cockpit with the contents of his stomach.

[PT20J]

58 minutes ago, Shadrach said:

I enjoy positive G aerobatics in appropriately rated aircraft. The rolls in the video were suboptimal (especially the second) to put it nicely. He either pulled too hard at the 180° mark or didn’t adequately pitch up st the start of the roll. He rolled out nose low and was likely accelerating rapidly when he began to arrest the descent.

I was thinking the same thing. The stock Mooney has a slow roll rate (which is why the original Predator wing and shorter flaps and longer ailerons - Maxwells have since replaced it with a wing off a K) and is very slick as Ross notes. All airplanes drop the nose in an aileron roll, and to avoid picking up excessive speed at the end it’s necessary to begin the maneuver very nose high in an airplane with a slow roll rate. In a Mooney it’s probably something like 60 deg nose up (I don’t know because I’ve never tried it). I only mention this because someone’s gonna try it. Watch a video of Bob Hoover rolling the Shrike and notice how much he pitches before beginning to roll. Hoover was so smooth that he claimed he never exceeded 2 g’s during his energy management routine. 

Like Ross, I prefer aerobatics in a Decathlon. 

Skip

[PT20J]

NACA report No. 772, August 1940, thoroughly explored the effect of mixture strength (including LOP) on BSFC, BHP, and CHT.

[Shadrach]

2 hours ago, PT20J said:

I was thinking the same thing. The stock Mooney has a slow roll rate (which is why the original Predator wing and shorter flaps and longer ailerons - Maxwells have since replaced it with a wing off a K) and is very slick as Ross notes. All airplanes drop the nose in an aileron roll, and to avoid picking up excessive speed at the end it’s necessary to begin the maneuver very nose high in an airplane with a slow roll rate. In a Mooney it’s probably something like 60 deg nose up (I don’t know because I’ve never tried it). I only mention this because someone’s gonna try it. Watch a video of Bob Hoover rolling the Shrike and notice how much he pitches before beginning to roll. Hoover was so smooth that he claimed he never exceeded 2 g’s during his energy management routine. 

Like Ross, I prefer aerobatics in a Decathlon. 

Skip

I have never seen a roll rate published for the Mooney but I would guess somewhere between  45° and 60°/sec depending on model and loading.

60° nose up is a lot.  As slow as the Mooney rolls, I don't think it would take that much initial pitch to roll out on altitude without without exceeding 1 g.

I say this because I've done aileron rolls in two airplanes with lousy roll rates, the Stearman N2S and a C150 Aerobat.  I only flew each of these aircraft only once, but they both had very modest roll rates for aerobatic aircraft (I'd guess similar or even less than my Mooney).  I recall using ~25°-30° in both. I checked the Aerobat manual which specifies 10-15° but I know we used considerably more than that.

 

[PT20J]

1 minute ago, Shadrach said:

I have never seen a roll rate published for the Mooney but I would guess somewhere between  45° and 60°/sec depending on model and loading.

60° nose up is a lot.  As slow as the Mooney rolls, I don't think it would take that much initial pitch to roll out on altitude without without exceeding 1 g.

I say this because I've done aileron rolls in two airplanes with lousy roll rates, the Stearman N2S and a C150 Aerobat.  I only flew each of these aircraft only once, but they both had very modest roll rates for aerobatic aircraft (I'd guess similar or even less than my Mooney).  I recall using ~25°-30° in both. I checked the Aerobat manual which specifies 10-15° but I know we used considerably more than that.

 

I measured it once many years ago when when gathering data for a flight simulator, but I don’t seem to have it any  more. The way to do it as suggested by a flight test engineer is to roll from a 60 deg bank to an opposite 60 deg bank and use a stopwatch to time from 45 deg to 45 deg. 

I agree that 60 is probably more than necessary, but it is safest to start with too much. The last airplane I rolled was a friend’s T-6G and it needed about 45 which surprised me - I guessed 30. 

Skip

[A64Pilot]

Not sure about roll rate but 60 degrees is WAY more than you think it is, go out and try it, if you pitch 60 down you’ll swear you pointing straight down.

20 to 30 is more like it and when you get over in your back or close to it, push forward on the control will raise the nose.

Bob Hoover could honestly roll the Shrike and maintain almost exactly 1G, but there are very few Bob Hoovers.

Look at the tray the glass is setting on, a little lip maybe but nothing holds it, then look at the tennis ball hanging under the tray, finally look at Bob, you can tell there is no real G.

Story is he rolled it with several AF Officers in back and they never knew it departed straight and level flight.

 

[A64Pilot]

Similar routine in a 114, and they are no hot rod

 

[Shadrach]

7 minutes ago, A64Pilot said:

Not sure about roll rate but 60 degrees is WAY more than you think it is, go out and try it, if you pitch 60 down you’ll swear you pointing straight down.

20 to 30 is more like it and when you get over in your back or close to it, push forward on the control will raise the nose.

Bob Hoover could honestly roll the Shrike and maintain almost exactly 1G, but there are very few Bob Hoovers.

Look at the tray the glass is setting on, a little lip maybe but nothing holds it, then look at the tennis ball hanging under the tray, finally look at Bob, you can tell there is no real G.

Story is he rolled it with several AF Officers in back and they never knew it departed straight and level flight.

 

For S’s and G’s I’ve rolled an airplane with the PNF holding a beverage. Perfect 1G not needed, just positive G throughout the maneuver. Pouring while you’re doing it would be a “wholenother” thing.

[Pinecone]

5 hours ago, A64Pilot said:

Not sure about roll rate but 60 degrees is WAY more than you think it is, go out and try it, if you pitch 60 down you’ll swear you pointing straight down.

20 to 30 is more like it and when you get over in your back or close to it, push forward on the control will raise the nose.

I have done 60 degree dive bombing. Yes, it seems like straight down.   Try this, look at the horizon.  Point up at a 60 degree angle.  That is where the horizon will be at 60 degrees nose low.

If you push forward inverted, that is a slow roll, not an aileron roll.

[Pinecone]

Yes, LOP was know in the 40s and 50s, but then forgotten when the airlines stopped flying the big radials.  I was just talking about this, this evening with my Dad.  He flew the AD, TBM/F, AF, and S-2 Tracker.  All radials.  And he was ASW so long loiter times was a good thing.  They ran LOP in cruise.

It was rediscovered in the 90s for GA.

 

[A64Pilot]

9 hours ago, Pinecone said:

I have done 60 degree dive bombing. Yes, it seems like straight down.   Try this, look at the horizon.  Point up at a 60 degree angle.  That is where the horizon will be at 60 degrees nose low.

If you push forward inverted, that is a slow roll, not an aileron roll.

By whatever name it’s what should be done in an aircraft with slower roll rates, like say a Mooney or the Aero Commander aircraft Bob Hoover was flying or you most likely will end up excessively nose down on recovery with speed getting away from you, necessitating a hard pull up possibly exceeding structural limits or the dive will build airspeed that can get into flutter and or exceed structural limits.

Take the Thrush Crop Duster, it has HUGE ailerons and therefore a very rapid initial roll rate, but those big ole wings also cause what’s called roll dampening, so it will fool you, you can snap into a 45 to 60 degree roll quickly then dampening kicks in and it won’t continue to accelerate its roll rate so it’s slow to roll, many very maneuverable aircraft just aren’t actually very good at aerobatics, so be careful. You would think Crop Dusters would be aerobatic bust most aren’t, they are more like dump trucks than sports cars.

Somebody used to do an aerobatic routine in a Grumman Agcat so I guess it is aerobatic or maybe they just knew what they were doing.

Highly modified, no hopper etc and wheel pants, fancy paint job it really didn’t even look like a Cat, but it was.

Much better to buy some spin and puke time with a pro in an aerobatic aircraft, and it could even save your life maybe if you find yourself in an unusual attitude someday, so it’s not just wasted money

[Pinecone]

1 hour ago, A64Pilot said:

By whatever name it’s what should be done in an aircraft with slower roll rates, like say a Mooney or the Aero Commander aircraft Bob Hoover was flying or you most likely will end up excessively nose down on recovery with speed getting away from you, necessitating a hard pull up possibly exceeding structural limits or the dive will build airspeed that can get into flutter and or exceed structural limits.

Nope.   You do NOT push in an aileron roll.

If Bob Hoover pushed, he would have spilled his tea.

An aileron roll and a barrel roll are all positive G.

I have been taught aerobatics on the civilian and the military side.  I had taught them on the civilian side, as well as upset and unusual attitude training.

I hope to be back doing mainly upset and unusual attitude training by next year.  No, not in a Mooney.