Mooney M20C vs Arrow 180

[AndreiC]

Just to bring my own experience with fuel to the discussion. The first plane I owned, N6085W, was a simple Cherokee 140. A few years after I sold it it was crashed due to fuel exhaustion, killing one and seriously injuring another. Myself, I once landed, at night, with 1.5 gallons usable fuel, thinking I had well over 10 gallons left. The next day I bought a fuel flow computer, and have been using one in every plane I owned religiously. 

The suggestion to start every flight with 30 gallons is not appealing to me. Even assuming you could know for sure you have exactly 30 gallons, which I doubt, that leaves 20 gallons to use after you take reserve into account. (For me the last 10 gallons are never to be touched.) With climb power burning 18 gph, that is a 1:45 flight at max. I bought this plane to travel long legs in one go, like Madison to Nashville. Why would I make a stop on such a trip?

[A64Pilot]

Went out and measured with a digital level, the C-140 was 225 degrees from full left to full right. Hard to tell exactly in the Cessna because cables don’t have the hard stop push pull tubes do.

My 81J was 78.7 degrees from full left to full right, now those just happen to be my only two aircraft and I’m sure the Cessna is greater than most, but it illustrates the point.

[A64Pilot]

15 minutes ago, Andrei Caldararu said:

Just to bring my own experience with fuel to the discussion. The first plane I owned, N6085W, was a simple Cherokee 140. A few years after I sold it it was crashed due to fuel exhaustion, killing one and seriously injuring another. Myself, I once landed, at night, with 1.5 gallons usable fuel, thinking I had well over 10 gallons left. The next day I bought a fuel flow computer, and have been using one in every plane I owned religiously. 

The suggestion to start every flight with 30 gallons is not appealing to me. Even assuming you could know for sure you have exactly 30 gallons, which I doubt, that leaves 20 gallons to use after you take reserve into account. (For me the last 10 gallons are never to be touched.) With climb power burning 18 gph, that is a 1:45 flight at max. I bought this plane to travel long legs in one go, like Madison to Nashville. Why would I make a stop on such a trip?

Yeah, in truth I’ll fly overgross before I leave fuel on the ground, assuming of course that I’m not coming out of a soft short grass strip of course.

AK FSDO has been granting 10% overload request from 135 operators forever and it’s just not been a problem, and 10% is a big number, in my J it’s I think 274 lbs? 

10 gls of gas is 60 lbs, yeah I’ll take off 60 lbs overgross and have an extra hour of fuel.

I’ve come very close to running out of fuel and it’s not comfortable, and most always preventable.

[PT20J]

I know, this is a Mooney site and we all like to think that every aspect of our airplanes is better than all the others. But airplane design is a series of tradeoffs. The Mooney is optimized for cruise efficiency. This leads to tradeoffs in other areas including the control system.

Cable controls, tensioned properly, don't have a lot of stretch or lost motion. But Mooney controls have a lot of rod ends in series which creates lost motion, especially as they inevitably wear, and this increases pilot workload. Cables operate on pulleys with bearings which have little friction. Mooney aileron push pull tubes run through a number of guide blocks which have greater friction (you do keep those well lubed, right?). In flight, especially at higher speeds, the ailerons tend to float up (that's why they should be statically rigged slightly down per the manual) and this puts the tubes in compression which flexes them and increases the friction through the blocks. There is only so much wing span and Mooney wanted a lot of flap to (probably to lower the landing speed) so the ailerons have a pretty short span for their area. This means an increased chord which increases the hinge moment requiring more control wheel force to move them. The lack of control wheel throw (probably to keep the wheel out of the way since the cabin is short in height to keep the drag low) doesn't help.

The elevator system suffers from friction at the instrument panel ball joint (most airplanes have this problem, but the Mooney seems worse than most). The gadgets placed in the elevator/trim system seem to reduce airspeed stability. I have flown many hours on long cross countries in a Cherokee (made longer by the fact that the airplane is slow) without an autopilot. I don't like flying my J for long periods without the autopilot -- it's a lot of work to hold altitude precisely. I think one problem people have landing is precise speed control which just seems to require more attention in a Mooney than many other airplanes. It's similar to a DC-3. This may be partially caused by the way the elevators are balanced. Most airplanes have overbalanced control surfaces for flutter avoidance. But the Mooney has underbalanced control surfaces. Who knows why? I asked a couple of aeronautical engineer friends and the best guess was to make the controls more responsive initially to changes in position since the underbalance will initially accelerate the control surface movement in the direction of applied control deflection.

And, then there is the aileron-rudder interconnect...

I've flown a lot of different airplanes. I like my J, but I'm realistic about the tradeoffs. The Cherokee was more fun to fool around in as was a C-152. The best harmonized controls were on the Beaver. I used to fly the Beaver for hours and never missed not having an autopilot. It was a joy to fly, but a float Beaver cruises at about the same speed as a C-150. Nothing beats my M20J for efficient cross country cruising, and I find the cockpit very comfortable for long trips. But, I'm glad for the autopilot.

Skip

[DCarlton]

1 hour ago, PT20J said:

I know, this is a Mooney site and we all like to think that every aspect of our airplanes is better than all the others. But airplane design is a series of tradeoffs. The Mooney is optimized for cruise efficiency. This leads to tradeoffs in other areas including the control system.

Cable controls, tensioned properly, don't have a lot of stretch or lost motion. But Mooney controls have a lot of rod ends in series which creates lost motion, especially as they inevitably wear, and this increases pilot workload. Cables operate on pulleys with bearings which have little friction. Mooney aileron push pull tubes run through a number of guide blocks which have greater friction (you do keep those well lubed, right?). In flight, especially at higher speeds, the ailerons tend to float up (that's why they should be statically rigged slightly down per the manual) and this puts the tubes in compression which flexes them and increases the friction through the blocks. There is only so much wing span and Mooney wanted a lot of flap to (probably to lower the landing speed) so the ailerons have a pretty short span for their area. This means an increased chord which increases the hinge moment requiring more control wheel force to move them. The lack of control wheel throw (probably to keep the wheel out of the way since the cabin is short in height to keep the drag low) doesn't help.

The elevator system suffers from friction at the instrument panel ball joint (most airplanes have this problem, but the Mooney seems worse than most). The gadgets placed in the elevator/trim system seem to reduce airspeed stability. I have flown many hours on long cross countries in a Cherokee (made longer by the fact that the airplane is slow) without an autopilot. I don't like flying my J for long periods without the autopilot -- it's a lot of work to hold altitude precisely. I think one problem people have landing is precise speed control which just seems to require more attention in a Mooney than many other airplanes. It's similar to a DC-3. This may be partially caused by the way the elevators are balanced. Most airplanes have overbalanced control surfaces for flutter avoidance. But the Mooney has underbalanced control surfaces. Who knows why? I asked a couple of aeronautical engineer friends and the best guess was to make the controls more responsive initially to changes in position since the underbalance will initially accelerate the control surface movement in the direction of applied control deflection.

And, then there is the aileron-rudder interconnect...

I've flown a lot of different airplanes. I like my J, but I'm realistic about the tradeoffs. The Cherokee was more fun to fool around in as was a C-152. The best harmonized controls were on the Beaver. I used to fly the Beaver for hours and never missed not having an autopilot. It was a joy to fly, but a float Beaver cruises at about the same speed as a C-150. Nothing beats my M20J for efficient cross country cruising, and I find the cockpit very comfortable for long trips. But, I'm glad for the autopilot.

Skip

Your analysis seems accurate but I don't think I've ever flown an aircraft with controls I preferred better than the Mooney's push pull tubes; particularly when in turbulence.  I've never considered the design as a trade off.  I've always felt like there was more "slop" or lost motion in a cable / pulley design.   I've only flown Pipers and Cessnas though (and that was a long time ago).  I do wish the elevator friction at the ball joint was better.

[PT20J]

Mooney's have a fairly slow roll rate as @A64Pilot noted. When designing the Predator, it didn't meet the Air Force requirements for roll rate, so Mooney cut down the flaps and lengthened the ailerons. I was working with Roger Hoh on a flight simulator project at the time and Roger (who is a handling qualities consultant and also developed the control laws for the HeliSAS for Robinson Helicopters) told me that the additional pressure on the push pull tubes caused them to bind so that the stick would stay wherever you put it -- there was no centering at all. Maxwells never flew the Predator with the original wing. Don told me that they replaced the wing with one from a scrapped K.

Handling qualities are difficult to quantify because they are subjective. If you fly the same airplane for years, it's qualities become normal to you. Back after WW II the NACA was trying to identify engineering specifications that would guarantee good handling qualities. They decided to take an airplane with qualities that a large number of pilots agreed were good and then measure it's stability and control characteristics. They chose the DC-3 because so many had been built and flown during the war and pilots generally thought it a good handling airplane. What they discovered is that it had some real quirks and was mildly longitudinally unstable in approach configuration under certain CG loadings.

Pilots generally liked the P-51. But when the 85 gallon fuselage tank was filled, the CG was behind the neutral point and the airplane was unstable in pitch to the point that instrument flight and aerobatics were prohibited by the flight manual until about half the tank was burned off. But the pilots just learned to deal with it and didn't seem to mind.

Skip

[EricJ]

1 hour ago, PT20J said:

Mooney's have a fairly slow roll rate as @A64Pilot noted. When designing the Predator, it didn't meet the Air Force requirements for roll rate, so Mooney cut down the flaps and lengthened the ailerons. I was working with Roger Hoh on a flight simulator project at the time and Roger (who is a handling qualities consultant and also developed the control laws for the HeliSAS for Robinson Helicopters) told me that the additional pressure on the push pull tubes caused them to bind so that the stick would stay wherever you put it -- there was no centering at all. Maxwells never flew the Predator with the original wing. Don told me that they replaced the wing with one from a scrapped K.

Handling qualities are difficult to quantify because they are subjective. If you fly the same airplane for years, it's qualities become normal to you. Back after WW II the NACA was trying to identify engineering specifications that would guarantee good handling qualities. They decided to take an airplane with qualities that a large number of pilots agreed were good and then measure it's stability and control characteristics. They chose the DC-3 because so many had been built and flown during the war and pilots generally thought it a good handling airplane. What they discovered is that it had some real quirks and was mildly longitudinally unstable in approach configuration under certain CG loadings.

Pilots generally liked the P-51. But when the 85 gallon fuselage tank was filled, the CG was behind the neutral point and the airplane was unstable in pitch to the point that instrument flight and aerobatics were prohibited by the flight manual until about half the tank was burned off. But the pilots just learned to deal with it and didn't seem to mind.

Skip

I recall reading some comments from a modern fighter pilot who got the opportunity to fly a P-51.    He'd been frequently told how well it handled and how light the controls were.   After flying it he said, "Compared to *what*?"   He thought the controls were very heavy and it was pretty mediocre handling.   He said he had no desire to fly it again. 

[Pinecone]

As for making sure you know how much fuel you have, get a FuelStik or Universal Fuel Hawk and calibrate it for YOUR airplane.   It does take very long (unless you have Monroy tanks) and then you can know exactly how much.  

Article on doing this - https://themooneyflyer.com/issues/2023-JulTMF.pdf

[Utah20Gflyer]

On 12/6/2023 at 8:14 AM, A64Pilot said:

Yeah, in truth I’ll fly overgross before I leave fuel on the ground, assuming of course that I’m not coming out of a soft short grass strip of course.

AK FSDO has been granting 10% overload request from 135 operators forever and it’s just not been a problem, and 10% is a big number, in my J it’s I think 274 lbs? 

10 gls of gas is 60 lbs, yeah I’ll take off 60 lbs overgross and have an extra hour of fuel.

I’ve come very close to running out of fuel and it’s not comfortable, and most always preventable.

You seem like a good candidate for CIES fuel senders, accurate to .1 gallon.   I feel like they increase the utility and safety of my airplane.  I have fuel flow as well with my JPI EDM 830 but that can’t account for a leak or other issue that increases the rate you are going through fuel.