Charlie Weight Conundrum

[cliffy]

In those airframes with "charlie weights" in the aft of the fuselage I wonder what Mooney found as far as 

how it affected the fore/aft polar moments in spin recovery?

I've never heard it discussed

Adding extra weight there "might" have deleterious affect on spin entry/recovery 

[Hank]

Since the Charlie weights are used to move the CG back into an acceptable location (memory says they are inly in models with the larger, heavier 6-cylinder engines), I thought their effect on spin recovery would be positive. I also thought that ALL Mooney Owners Manuals / POHs have some version of "spins are not approved" written in the FAA-approved portion.

As for affecting the entry into a prohibited maneuver, stay away from the lower edge of the flight envelope and you won't enter; if you do, the Charlie weights are supposed to enable you to regain control vs. not having the Charlie weights.

[A64Pilot]

7 hours ago, cliffy said:

In those airframes with "charlie weights" in the aft of the fuselage I wonder what Mooney found as far as 

how it affected the fore/aft polar moments in spin recovery?

I've never heard it discussed

Adding extra weight there "might" have deleterious affect on spin entry/recovery 

It would, just as the heavier engine in the nose does, or wing tip tanks like on Bonanza’s.

Spins I think have lost the concern they used to have maybe because it seems that inadvertent spins that occur at recoverable altitudes are exceedingly rare.

Having said that even aircraft that spins aren’t allowed are usually spin tested. I say usually because I’ve heard of major modifications where the FAA required it, and times when they didn’t. I talked to the test pilot that flew the cert tests for the -10 engine STC on a Caravan and apparently he had to spin it several times.

There used to be a video of a NASA test pilot spinning a V tail Bo, when he entered a spin with opposite aileron it quickly wrapped up and he had to jump as it wasn’t recoverable, interestingly that video was removed from the internet. Interesting to me because I think most inadvertent spins will begin with opposite aileron input. No wing tanks on this Bo either.

I never had to spin any Thrush in any of the Certifications we did, and never asked why, because I had no desire to. Maybe it’s because the FAA realized that any spin a crop duster was likely to get into was well below min recovery altitude?

Anyone know if the big Mooney’s were ever spin tested? I have no idea. We seem to have a pretty good sized vertical and there seems to be a correlation between spin recovery and size of the vertical / rudder, so maybe we recover well? 

[Hank]

41 minutes ago, A64Pilot said:

Anyone know if the big Mooney’s were ever spin tested? I have no idea. We seem to have a pretty good sized vertical and there seems to be a correlation between spin recovery and size of the vertical / rudder, so maybe we recover well? 

No idea about the big Mooneys, but this is what my Owners Manual says about spins. Last I checked, we all have the same vertical tail and rudder, except the early models with the short rudder (my rudder goes all the way down).

This does not sound like "we recover well" to me. What does the Long Body POH have to say?

[A64Pilot]

22 minutes ago, Hank said:

No idea about the big Mooneys, but this is what my Owners Manual says about spins. Last I checked, we all have the same vertical tail and rudder, except the early models with the short rudder (my rudder goes all the way down).

This does not sound like "we recover well" to me. What does the Long Body POH have to say?

It doesn’t, maybe but does seem to me to indicate that it was fully tested, by fully it seems the test pilot allowed the spin to fully develop, which I don’t think the FAA requires, from memory they only require one turn.

Spin testing is eventually done at worst case as in max aft CG and max gross weight, and I think most of us are most often fwd CG.

It seems that the more modern a design is, the less spin resistant it is. I should have said the less likely to recover easily as I think the Cirrus is very spin resistant. My test pilot mentor told me to be very cautious with aircraft that were spin resistant as often they were hard to recover. Easy in, easy out he said. I think maybe because back in the day spins were thought of as a sort of normal maneuver and everyone was taught to spin and recover.

Anyway the C-210 I used to have in a power on stall, and I mean relatively low cruise power if you stalled it, it would spin, you couldn’t stop it. I knew it was going to be ugly because before the stall the rudder was buried and the ball was coming out of center, but I didn’t expect it to roll over on its back and start to rotate. I didn’t spin it as I pulled power as soon as it went over on its back, but it shocked me because I thought all Cessna’s were benign, gentle things. But the 210 has a laminar flow wing too where most other Cessna’s don’t, maybe that plays into it?

I’ve got a video of me spinning my little C-140 somewhere a long time ago, it too goes over on its back and comes out spinning, but you can spin it until you puke and it will recover almost instantly when you want it too, very good spin trainer. But it has very high rudder authority, I think tail wheel aircraft have to, and when nose wheels began to be designed the require t for rudder authority is much less and they are harder to recover from a spin, I know the 210 doesn’t even have enough rudder to keep in trim when approaching a power on stall. A theory of mine, tailwheel vs nose wheel that is.

[cliffy]

My Commercial ticket check ride consisted of 2 turns about a point and 4 spins in my 1946 Cessna 140. 

I spun it many times

I talked with Bill Wheat once and he related that he got into a 5 turn spin in a Mooney and didn't think 

he was going to get out of it. Said he'd never do it again.

Polar moments play a big roll in spin recovery after rotation is established (IMO). 

"They all fly through the same air" as Al Mooney said but a lot of things play into the dynamics

of aircraft control

[Fly Boomer]

3 hours ago, A64Pilot said:

It would, just as the heavier engine in the nose does, or wing tip tanks like on Bonanza’s.

Spins I think have lost the concern they used to have maybe because it seems that inadvertent spins that occur at recoverable altitudes are exceedingly rare.

Having said that even aircraft that spins aren’t allowed are usually spin tested. I say usually because I’ve heard of major modifications where the FAA required it, and times when they didn’t. I talked to the test pilot that flew the cert tests for the -10 engine STC on a Caravan and apparently he had to spin it several times.

There used to be a video of a NASA test pilot spinning a V tail Bo, when he entered a spin with opposite aileron it quickly wrapped up and he had to jump as it wasn’t recoverable, interestingly that video was removed from the internet. Interesting to me because I think most inadvertent spins will begin with opposite aileron input. No wing tanks on this Bo either.

I never had to spin any Thrush in any of the Certifications we did, and never asked why, because I had no desire to. Maybe it’s because the FAA realized that any spin a crop duster was likely to get into was well below min recovery altitude?

Anyone know if the big Mooney’s were ever spin tested? I have no idea. We seem to have a pretty good sized vertical and there seems to be a correlation between spin recovery and size of the vertical / rudder, so maybe we recover well? 

Rich Stowell tested an early Mooney.  At least for the airplane he tested, he clearly answers the question "maybe we recover well".  The answer is "no".  Maybe even "hell no".  Here is his summary of some of the POH language:

"A tremendous amount of altitude is lost during the one-turn spin and recovery process.  Occupants are likely to become disoriented.  Unrecoverable flat spins are possible.  Can the warnings against spinning the airplane be any clearer than this?  But if you do inadvertently, NASA Standard actions are the remedy."

[M20F]

2 hours ago, cliffy said:

I talked with Bill Wheat once and he related that he got into a 5 turn spin in a Mooney and didn't think 

he was going to get out of it. Said he'd never do it again.

In the mid 80’s friend of mine was messing around with Wally Sedgwick (50000hr WWII pilot, legendary Chicago DPE in the day).  They went up to spin a C and got 2 spins and into a spiral.  Burned 5000’ in the recovery.  Wally said it scared him more than any event in his life including having people shoot at him.  Neither of them have any idea how they got out of it.  
 
Spins are an acrobatic maneuver.  Spins can lead to spirals which kill you (if you release the back pressure it is going to go to a spin in just about anything I have flown that can spin).  On a 150 with a good engine you can get it to spin (weak engine it is just going to stall and roll a bit) and there is a video of one of Bill Kershner’s CFI’s spinning one down from 18000’.  Planes like a Mooney aren’t going to hold the spin, you lose control authority and at that point you are along for the ride hoping an air pocket or something knocks it out.  
 

Vne and beyond comes very fast in a spiral and if you aren’t careful on the exit, off comes pieces (like the wing). 
 
In short fun maneuver in gliders, 150’s, and the like.  There is a reason though why some planes shouldn’t be spun.  
 

Rolls in a Mooney are a totally different story but I wouldn’t know anything about that…..

[cliffy]

My instructor had me doing spins way before my PP ride in a 150  I enjoyed them

Back in the biplane days with no instruments, it was taught that if one was caught above a cloud deck

and knew that there was room underneath that the way to get down was to go into a spin and hold it 

through the clouds.

Once you broke out you got out of the spin.

You always knew what condition you were in in a spin in IMC

 

[PT20J]

What I believe @cliffy was alluding to in the original post is that CG is only one parameter. Moment of inertia is also a consideration. A bowling ball and a bowling ball cut in half with each half mounted to opposite ends of a three foot pipe both have that same CG but very different moments of inertia. Once the second object begins spinning about it's CG, it will resist attempts to stop the spin.

[cliffy]

BINGO!

The casual discussion of adding "charlie weight" to cure a too far fwd CG has more to consider than just  fore/aft balance. 

Consider two airplanes -one with low polar moment longitudinally and another with high fore/aft polar moment

BUT-

both with the same vertical fin and rudder-

The higher polar moment a/c will have less ability to recover from any yawing upset spin or no spin.

One just can't add charlie weight if not provided for by the factory in testing. 

Other treads brought my attention to this subject. 

 

[Pinecone]

But also remember, higher polar moment of inertia is harder to get spinning.