M20J Main Gear Tire and Tube Recommendations

[1980Mooney]

5 hours ago, jetdriven said:

The tires are 125$ but the tubes are 200$. So changing them twice as often is false economy. 

Right.  I think what you are inferring is that the tubes should be changed every time the tire is changed.  It can get pinched during reinstallation or weakened as it flattens/spreads out a second time.  It is better to have tire treads that last 2X without disturbing the expensive Airstop tube.  When I was younger I used to change my own tires and tubes.  I would try to reuse tubes and generally had good luck.  However now I let my A&P do it.  He will not re-use tubes under any circumstances due to failure rate.

[1980Mooney]

5 hours ago, EricJ said:

I just today took this pic of mine, since I just put a new tire and Michelin airstop tube on that gear and wanted to make a record to track any tire slippage.    This is the TR-20 as bought from AS.

Won't a glance at the red spot immediately tell you if your tires have experienced any slippage on the wheel?  I know the red dot is supposed to represent the lightest point for balancing and should be immediately adjacent the stem.  No need for a picture.

[EricJ]

1 minute ago, 1980Mooney said:

Won't a glance at the red spot immediately tell you if your tires have experienced any slippage on the wheel?  I know the red dot is supposed to represent the lightest point for balancing and should be immediately adjacent the stem.  No need for a picture.

Yes, but for me having the pic to confirm exactly where the red spot was is useful.   The cost of a pic is insignificant compared to my ability to forget easy stuff. 

[Will.iam]

11 hours ago, EricJ said:

I agree, and it's almost reflex for me to put the flaps up on rollout once the airplane is stable on the ground.   I fly C182s with an organization (CAP) and that's what our local ops guys teach, so there's compatibility there.   I was helping relocate some airplanes and flying left seat in another squadron's airplane with one of their guys, and he got very upset when I brought the flaps up on rollout at their airport, going on about how that's how people retract the gear on the runway so it's unsafe, etc., etc.   There are still those who think it's a bad idea. 

 

To which i would replay that’s why there is object form convention. I. E. The gear handle is round and the flap handle is flat. This is so you don’t confuse the 2 even if it’s completely dark you know by feel alone which is which. Mooney goes a step further by placing the gear up high in the panel with flaps low. If that instructor has a problem with which is which maybe flying is not for him in retracts. 
 

maybe show him this article:

 

Shape Coding 

 

During World War II, the United States Army Air Corps faced a critical issue with its B-17 bombers: a high rate of landing accidents due to pilots retracting the landing gear instead of the flaps during landing. This recurring problem not only resulted in the loss of aircraft and costly repairs but also put the lives of pilots and crew members at risk. In an effort to address this issue, the Army Air Corps turned to a young aviation psychologist named Alphonse Chapanis, whose groundbreaking work would revolutionize cockpit design and significantly improve aviation safety.

 

During World War II, the B-17 Flying Fortress, a heavy bomber crucial to the war effort, was notorious for landing incidents where pilots would mistakenly activate the landing gear lever instead of the flap lever. Both levers were located in close proximity and had similar designs, making it easy for pilots, especially under the stress of combat and fatigue, to confuse them. This confusion led to the catastrophic consequence of the plane's wheels being retracted upon touchdown, causing the aircraft to skid along the runway. This recurring problem not only resulted in the loss of aircraft and costly repairs but also put the lives of pilots and crew members at risk. In an effort to address this issue, the Army Air Corps turned to a young aviation psychologist named Alphonse Chapanis, whose groundbreaking work would revolutionize cockpit design and significantly improve aviation safety.

 

Alphonse Chapanis, a pioneer in the field of human factors engineering, recognized the problem as one of design rather than pilot error. He theorized that by making the controls more distinguishable through both visual and tactile cues, pilots would be less likely to make such critical mistakes. This led to the development of shape coding, a simple yet ingenious concept that involved assigning distinct shapes to different controls.

 

One of the most famous examples of shape coding implemented by Chapanis was the addition of a wheel-shaped grip to the end of the landing gear lever. This unique shape not only provided a clear visual indicator but also a tactile cue that pilots could easily recognize even in low-light conditions or when their attention was divided. By simply feeling the shape of the lever, pilots could confidently identify and operate the correct control.

 

Chapanis' shape coding solution proved to be highly effective in reducing landing gear-related accidents. It was quickly adopted for the B-17 and other aircraft, leading to a significant improvement in aviation safety. The success of shape coding also paved the way for further advancements in cockpit design, with human factors engineering becoming an integral part of aircraft development.

 

Today, shape coding is a standard practice in aviation and other industries where human-machine interaction is critical. It has been incorporated into various controls, from aircraft cockpits to industrial machinery, to ensure that operators can quickly and accurately identify and operate the correct controls.

 

The importance of shape coding for aviation safety has been recognized by regulatory bodies worldwide. In the United States, the FAA has incorporated shape coding requirements into its regulations, specifically in Part 25 of the Federal Aviation Regulations, which governs the airworthiness standards for transport category airplanes. This regulation mandates the use of distinct shapes for certain critical controls, including the landing gear lever, to prevent accidental operation and ensure safe flight operations.

[jetdriven]

You would think that shape coding would eliminate gear retraction on rollout, but in fact, it happens quite often. And the results are pretty devastating. But if you don’t start grabbing stuff without actually paying attention and looking at it, you can’t put the gear up on the runway. But runway ops are the definition of a critical phase of flight. The first Culver cadet delivered from the factory had an interlock to where if the  gear wasn’t down, The throttle could not be pulled back less than 1/3, and the factory pilot came in and realized that he couldn’t pull the throttle back far enough, so he turned the key on and geared up the first one. And we’ve still haven’t invented anything that’s idiot proof yet.  

[Fly Boomer]

21 minutes ago, jetdriven said:

You would think that shape coding would eliminate gear retraction on rollout, but in fact, it happens quite often.

Why doesn't the gear safety switch prevent that?

[1980Mooney]

41 minutes ago, Fly Boomer said:

Why doesn't the gear safety switch prevent that?

There were 2 different approaches to this. Early designs used squat switches. Later used an air safety switch. 
 

With squat switches, if you hit a good bump while taxiing or a momentary gust while rolling on takeoff, the switches may unload and sense as if the plane was airborne. Or a switch might be defective and stuck sensing airborne all the time. 
 

With airspeed safety switches, they can be miscalibrated to a low speed or defective and stuck sensing airspeed. 
 

In either case if the lever is up while fast taxiing or in high speed roll on takeoff, the gear could collapse 
 

 

Edited August 27 by 1980Mooney

[EricJ]

All of CAPs aircraft are fixed-gear, so it's totally a non-issue for them.    I think it's just one of those topics that some people get passionate about.   In this case it's interesting that there's the pragmatic "raise the flaps and save the tires" side, and the "there's a slight chance that'll cause a problem" side, that both have useful points, they're just not weighted equally by most.

[cliffy]

3 stories-

Twin Beech has main wheels that protrude below the engine cowl so that the airplane will roll to a stop on them.

One Twin Beech many years ago did this at KVNY because the pilot had a habit of throwing the gear switch up just prior to throttles fwd so the gear came up as he lifted off, I saw the airplane sitting on its sucked up wheels on 16R with bent props

The Culver Cadet early on also had a wig-wag arm that came up and waved in front of the pilot if the power was pulled off and the gear still up.

I wonder how many early Bonanzas  have gone gear up after landing because a Piper driver was flying it and went to pull the flaps up and reached to the right side of the throttle quadrant and pulled the gear instead? Seems "shape" design might not be the only cockpit design idea that needed to be done. 

[Pinecone]

I feel Mooney got it right with the distinct position of the two switches.  No way you will accidentally actuate the gear switch from leaning over and reaching down.

A-10 was similar with gear handle on the panel and the flap switch along side aft of the throttles.

[jetdriven]

It’s a really great design and a really great idea, and the switch placement is ideal, but it still happens.

[hubcap]

I was trained to raise the flaps after achieving ground control and I still do it that way.

Myrtle's flap switch is down below the red knob for mixture control, and my gear switch is up at 12:00 just below the glare shield. Seems like adequate separation to me.

[Hank]

19 hours ago, Will.iam said:

Retract the flaps before applying the brakes will significantly lower your chances of locking up the brakes and flat spotting a tire. 

 

7 hours ago, Will.iam said:

... that’s why there is object form convention. I. E. The gear handle is round and the flap handle is flat... Mooney goes a step further by placing the gear up high in the panel with flaps low.

 

15 minutes ago, hubcap said:

I was trained to raise the flaps after achieving ground control and I still do it that way.

Myrtle's flap switch is down below the red knob for mixture control, and my gear switch is up at 12:00 just below the glare shield. Seems like adequate separation to me.

After landing, while holding the throttle to idle, I reach out a finger and raise the flaps. To reach the Gear switch, I have to let go and reach up to the top of the panel.

Raising the flaps reduces lift and puts weight on the tires. I prefer to not brake until slowing to 50 mph. So far, no flat spots that I'm aware of in 17 years of doing this.

[Will.iam]

1 hour ago, jetdriven said:

It’s a really great design and a really great idea, and the switch placement is ideal, but it still happens.

Yes it can and still will happen but the more

techniques you have in place to prevent that the more odds are ever in your favor. 

[Pinecone]

My flap switch is way down on the center console.  So a LONG ways from the gear switch.

Yes, it still happens, but a lot less than on other makes and models.

[jetdriven]

That also brings up a another point.  Transition to a different airplane. Rarely will you only fly this exact airplane the rest of your flying career.  So you get into a piper arrow, or a Bonanza, and since your SOP is to put the flaps up to get weight on the wheels, you try that.

[PT20J]

On 8/27/2024 at 6:18 AM, Fly Boomer said:

Why doesn't the gear safety switch prevent that?

Excellent question. From the M20J Service Manual: