98 Allegro vs 1980 M20J

[carusoam]

33 minutes ago, 0TreeLemur said:

After 5 years of flying a C and now flying a J, I can attest that getting the tip vortex off the aileron makes the J feel much more nimble in roll compared to the C.

How is the transition going?

biggest things that I encountered were more power and weight issues… going form C to O…

and really knowing my C’s performance… compared to the O…

My C was extremely worn… compared to my O…

Short field landings in the M20C were really short… the O were just kinda short….  

Best regards,

-a-

[Pinecone]

31 minutes ago, PT20J said:

I owned a 1978 J (squared off wingtips) 30 years ago and now own a 1994 J (sculpted wingtips). It's been too long for me to compare aileron forces, but I did notice something else:. In the older airplane, both ailerons tended to float up a slight bit during cruise, and I don't notice this with the later model.

That can also be a function of rigging.

I have been told that some experienced riggers, rig the ailerons to be slightly training edge up in cruise and that this increases cruise speed.

No idea if this is correct.  But mine are rigged that way (came that way to me).

[PT20J]

6 minutes ago, DCarlton said:

Beveled trailing edges?   

[PT20J]

1 minute ago, Pinecone said:

That can also be a function of rigging.

I have been told that some experienced riggers, rig the ailerons to be slightly training edge up in cruise and that this increases cruise speed.

No idea if this is correct.  But mine are rigged that way (came that way to me).

What I was speaking of is the tendency of the ailerons to float up from their static rigging during flight. This was a problem with the Predator. I knew the test pilot at the time that flew it and he told me that the ailerons floated up so much at high speed that they flexed the push-pull tubes to the point where they would bind on the guide blocks and the stick would stay pretty much wherever you put it. 

The Mooney M20J maintenance manual calls for the aileron rigging to be 0 to -2 deg down. 

[DCarlton]

15 minutes ago, Pinecone said:

That can also be a function of rigging.

I have been told that some experienced riggers, rig the ailerons to be slightly training edge up in cruise and that this increases cruise speed.

No idea if this is correct.  But mine are rigged that way (came that way to me).

Interesting.  I've wondered about mine for years.  I'll look over at one wing in cruise and think the plane is out of trim, then look over at the other wing, and both ailerons looks a tad high.  Nice to know my plane is "normal".  It seems to be rigged nicely; about 153 kts typical in cruise.  

[DCarlton]

16 minutes ago, PT20J said:

What I was speaking of is the tendency of the ailerons to float up from their static rigging during flight. This was a problem with the Predator. I knew the test pilot at the time that flew it and he told me that the ailerons floated up so much at high speed that they flexed the push-pull tubes to the point where they would bind on the guide blocks and the stick would stay pretty much wherever you put it. 

The Mooney M20J maintenance manual calls for the aileron rigging to be 0 to -2 deg down. 

Curious now how you measure within a couple of degrees.  Will take a look at the manual.  

[skykrawler]

2 hours ago, PT20J said:

What I was speaking of is the tendency of the ailerons to float up from their static rigging during flight. This was a problem with the Predator. I knew the test pilot at the time that flew it and he told me that the ailerons floated up so much at high speed that they flexed the push-pull tubes to the point where they would bind on the guide blocks and the stick would stay pretty much wherever you put it. 

The Mooney M20J maintenance manual calls for the aileron rigging to be 0 to -2 deg down. 

I find this hard to believe.  A 'faired' surface generating enough hinge moment to flex tubes enough to bind.  If that was the case then deflecting the surface with the wheel would also cause it to bind.   Perhaps this was when performing aerobatic maneuvering (higher G force flexing the wing)  which may have been a requirement for a military trainer.

[PT20J]

33 minutes ago, skykrawler said:

I find this hard to believe.  A 'faired' surface generating enough hinge moment to flex tubes enough to bind.  If that was the case then deflecting the surface with the wheel would also cause it to bind.   Perhaps this was when performing aerobatic maneuvering (higher G force flexing the wing)  which may have been a requirement for a military trainer.

Roger didn't tell me the exact test conditions, but it was probably in a dive. Roger Hoh is a handling qualities engineer hired by Mooney to try to get the handling qualities of the Predator acceptable. 

Even in normal operation, the tubes rub a bit on the outboard block because the motion at the outboard end is partially fore-aft due to the aileron bellcrank pivot. It might not take much to bind. 

[A64Pilot]

On 1/15/2023 at 11:36 AM, Pinecone said:

That can also be a function of rigging.

I have been told that some experienced riggers, rig the ailerons to be slightly training edge up in cruise and that this increases cruise speed.

No idea if this is correct.  But mine are rigged that way (came that way to me).

I’ve done the first flight of a few hundred aircraft, I found that with the trailing edges of the ailerons set dead even on the ground, they would fly about 1/4” trailing edge high, I’ve adjusted them to fly even in flight, only thing I noticed was the aircraft was heavier in the roll axis. But ailerons rigged even on the ground will be “sucked up” in flight, any slight looseness in the system will allow them to fly high, I think it’s entirely normal and correct.

Some Ag guys will droop their ailerons to try to get off shorter, and it makes them real heavy on the ailerons.

From track and balancing helicopter rotor systems bending a trim tab up had less effect than bending one down, I believe the air above a wing is less dense than air beneath, higher velocity, but in a vacuum, so less dense, so yes there should be less drag.

I never did speed runs, just isn’t as important on an Ag plane but if I had to bet I’d bet there is a slight speed increase.

It also washes the wing out slightly, meaning it’s less likely to tip stall, and tip stalls are bad of course

[A64Pilot]

On 1/15/2023 at 12:03 PM, DCarlton said:

Curious now how you measure within a couple of degrees.  Will take a look at the manual.  

Cheap electronic level will get you much closer than 1 degree, even a cell phone will

[A64Pilot]

On 1/15/2023 at 2:58 PM, PT20J said:

Roger didn't tell me the exact test conditions, but it was probably in a dive. Roger Hoh is a handling qualities engineer hired by Mooney to try to get the handling qualities of the Predator acceptable. 

Even in normal operation, the tubes rub a bit on the outboard block because the motion at the outboard end is partially fore-aft due to the aileron bellcrank pivot. It might not take much to bind. 

The faster you go, the more the ailerons are “sucked up”. It’s an actual vacuum

[KSMooniac]

FYI, my understanding of the Predator is that the control system was quite different than a normal M20, and even had some bellcranks with adjustment provisions to change throws/forces/range of motion, etc.  It was an R&D vehicle of course.  I believe Maxwell returned it to stock M20K configuration during the restoration.