"Positive Rate, Brakes"

[Threefingeredjack]

One of my instructors told me he gave a flight review to a guy who put the gear switch up before starting the takeoff roll, and let the squat/weight-on-wheels switch start the retraction process.

Yeah. Good plan.

 

[dtuuri]

When you apply the brakes the force that changes the angular momentum of the tires is transmitted from the hub to the tires. When you touch down, the force that changes the angular momentum of the tires is transmitted from the ground to the tires. Of course, there would also be some force transmitted from the tire to the hub on touchdown, but I'm guessing that the hubs have less angular inertia than the tires.

However, another question that comes to mind is, "Do you have to be careful about shearing the valve stems off when applying the brakes after touchdown?"

This all sounds like a good thing to occupy my mind while trying to fall asleep. Until then, I think I'm going to satisfy myself that the centrifugal force probably stretches the tire away from the rim, so there's less friction to hold the tire to the rim after takeoff. How's that sound to an engineer?

dtuuri

 

[Henning]

I'm curious why they don't shear when it touches down?

dtuuri

Because the mass of the tire is much greater than the mass of the hub. In the touch down the ground changes the tire's inertial moment, in the take off tap the hub bead absorbs the tires inertial moment.

This is why locking screws are used in high torque, high traction operations like drag racing and rock crawling.

 

[dtuuri]

Because the mass of the tire is much greater than the mass of the hub. In the touch down the ground changes the tire's inertial moment, in the take off tap the hub bead absorbs the tires inertial moment.

This is why locking screws are used in high torque, high traction operations like drag racing and rock crawling.

Aw shucks. I think I'm getting it. Here I thought I had found a cure for insomnia. There's a 'reason' I'm not an engineer.

dtuuri

 

[gismo]

Reason that they will shear in the air is that the multi-disc brakes on the B-25 are ridiculously effective and the momentum/weight of the tire (very large wheels) will keep it moving while the wheel stopps instantly. At least that is what we were told in training...never had a desire to test it.

I'm very skeptical about that issue, but then I'm not the one paying for B-25 tubes either. Seems to me that while the wheels will indeed stop much more quickly/abruptly in the air, the amount of torque applied by the wheel to the tire cannot be any higher with an airborne tap of the brakes than what's generated when braking with the same pedal pressure on the ground. And it ought to be the torque that's correlated with the force trying to slip the tire on the wheel, not the acceleration. So I think this is very likely just an OWT, supported by valve stem problems that were probably caused by underinflated tires and/or more aggressive braking than the system was designed to tolerate without tire slippage.

 

[Captain]

Another angle to look at is the simple fact that brakes aren't applied on the landing roll until relatively low speed where a 'brake tap' would happen at a much higher tire speed.

Takeoff is never at full flaps and landing usually is. Gear retraction happens pretty quick after liftoff where brake application after landing is quite a ways down the road.

 

[Henning]

Aw shucks. I think I'm getting it. Here I thought I had found a cure for insomnia. There's a 'reason' I'm not an engineer.

dtuuri

Glad to help... Now have you heard the one about the airplane on the treadmill? Can it take off?

 

[MassPilot]

There have been a few times when I felt a fairly strong vibration immediately after rotation. I tapped the brakes and it went away.

 

[Capt. Geoffrey Thorpe]

I already have to call speeds; "Takeoff power set,airspeed alive,40,Vr, rotate, positive rate, brakes," why not "gear up?"

And this is the reason that people think it is hard to fly a taildragger.

And why my &%#(@ insurance is as high as it is - Pilots with their head down while rolling on the runway.

"What was that sound?"

"You just took out a runway light."

​

You will have a lot to unlearn if you ever make a tailwheel transition.

 

[Henning]

There have been a few times when I felt a fairly strong vibration immediately after rotation. I tapped the brakes and it went away.

That means what? Two things, you check the tire for serious damage and the bearing for proper preload. If it's a rental you squawk it on return if you return. On that plane, continue tapping lol.

 

[MassPilot]

That means what? Two things, you check the tire for serious damage and the bearing for proper preload. If it's a rental you squawk it on return if you return. On that plane, continue tapping lol.

I'm a renter. I never thought of it being an indication of a problem. I figured that once in a while they hit a resonance frequency or something. If it happens again, I'll make sure to let the FBO know.

 

[Jaybird180]

This thread is waaaaay too long

 

[Henning]

Not really, the post above yours shows that positive learning was still occurring.

If you mean there were many posts in between that were unproductive, meh, whatcha wanna do?

 

[Jaybird180]

I forgot to add my smilie. I learned something too, which I why I read all the posts before replying.

 

[Henning]

I'm a renter. I never thought of it being an indication of a problem. I figured that once in a while they hit a resonance frequency or something. If it happens again, I'll make sure to let the FBO know.

Here's a test as to whether it needs immediate service or not:
Shake the plane sideways while observing the gear, if you can see a shifting in alignment you are shut down until serviced. This is a minimum skill service to learn BTW, any A&P will be glad to check you out on it. If that all looks solid then look at the tire for flat spots, if you see it take a picture ASAP and call in you had a shake on take off and found a flat spotted tire on landing. The question you will face is "why did you continue without calling or landing back?"

Any vibration, shake or rattle indicates a potentially hazardous condition that needs to be cleared before further ops. If you have a bad/loose bearing not good. If you have a flat spot, not particularly hazardous with a small plane even if it blows; however you don't want to buy the tire either.

 

[Jaybird180]

Here's a test as to whether it needs immediate service or not:
Shake the plane sideways while observing the gear, if you can see a shifting in alignment you are shut down until serviced. This is a minimum skill service to learn BTW, any A&P will be glad to check you out on it. If that all looks solid then look at the tire for flat spots, if you see it take a picture ASAP and call in you had a shake on take off and found a flat spotted tire on landing. The question you will face is "why did you continue without calling or landing back?"

Any vibration, shake or rattle indicates a potentially hazardous condition that needs to be cleared before further ops. If you have a bad/loose bearing not good. If you have a flat spot, not particularly hazardous with a small plane even if it blows; however you don't want to buy the tire either.

The 182P I got my HP in would remind you it's at Vr with a nose gear rattle. I thought it was cute

 

[bigblockz8]

I would not strongly argue you point, but most pilots I see show residuals of how they were initially trained. Most were trained to use a checklist on the ground but not after takeoff, which means that almost none use them in the air at all except at checkride time. When they do use them, they have to haul out the sheet of paper.
The point I was making, maybe I'm stuck on this, is that we CFI's do a pathetic job of teaching a lot of these habits because we don't integrate them into our training.

Not to sound stupid but does taking off and then reducing to cruise power count as a checklist? That and flaps up if used. I only use the checklist when on the ground, before takeoff and after landing. I cannot tell you what the list even says about climb,cruise,etc.

 

[Skip Miller]

According to this thread, at least the nosewheel will continue to rotate in some planes....

-Skip

http://www.pilotsofamerica.com/forum/showthread.php?p=912234&highlight=rotate#post912234

 

[DavidWhite]

Checklists have their purpose.....that place isnt immediately after rotation in the mighty Cessna 172.

I seem to do ok........

 

[denverpilot]

That means what? Two things, you check the tire for serious damage and the bearing for proper preload. If it's a rental you squawk it on return if you return. On that plane, continue tapping lol.

There are a lot of FBOs who'd just ignore the squawk. BTDT. One locally here used to take troubleshooting costs out of a CFI's pay if the problem couldn't be found.

There's been significant changes at that one, so hopefully that went away. Not a good Safety culture at all.

 

[Henning]

There are a lot of FBOs who'd just ignore the squawk. BTDT. One locally here used to take troubleshooting costs out of a CFI's pay if the problem couldn't be found.

There's been significant changes at that one, so hopefully that went away. Not a good Safety culture at all.

This is one of the main reasons people buy planes, quality control.

 

[BillTIZ]

One of my instructors told me he gave a flight review to a guy who put the gear switch up before starting the takeoff roll, and let the squat/weight-on-wheels switch start the retraction process.

I would highly document the discussion during the ground portion of the flight review on his actions. I'd also print out some accident reports of aircraft that settled and dinged the prop after the gear started a premature retraction.

That squat switch just slightly off and that gear could retract as soon as you got light in the tires but not off the ground.

 

[GCA319]

Yep, I know.

I was mainly targeting explaining that the OP doesn't need to feel silly about "unnecessary" callouts if they'll serve him well later on.

And since I fly for recreation, not a living... I seriously doubt I will ever do twin transition training.

It'd be a waste of time and money with the mixture of twin insurance industry behaivior, and the need for a pretty darn beefy twin to drag yourself back aloft up here. (Or flying it around half empty all the time to maintain reasonable safety margins...)

Never say never and all that, but it's way down the list of possible things I'd spend serious bucks on.

Absolutely. If a pilot who fly's for fun were to ask about doing MEL training just for the heck of it (meaning, no plans for buying a twin), I'd tell them to get a Glider or SES rating instead.

 

[GCA319]

I see how it could come in handy down the road. Just feels odd. It's like playing dress up mentally. Let's pretend that this 172 is a 727. Feels odd mentally. Same way that one school I looked into required students to wear a uniform with two stripes. I'm not a commercial student after all so why have the silly mentality of "I am a captain" or whatever when we could focus on other things such as why I am drifting off heading vs. whether I did call-outs and tapped the brakes?

I neglected to mention how I turn into a GPWS in the pattern. Another thing I don't get. It's a bit much to call 100,50,40,30,20,10 while trying to learn to land. Watch any student try handling radios for the first time and you'll see why 1000ft and 125 degrees turns into 1400 and 300, I know that I did worse.

They have primary students staring at the altimeter making call outs while learning to land? great. Let me guess, they also have you set "climb thrust" at 500'....And they also have you keep the airplane rolling as long as possible so you can call out 80 knots. My advice for you is to look for another flight school that will teach you what you will need to know to safely fly a light GA airplane in a single pilot operation, not how to fly a 172 like a CRJ.

 

[GCA319]

There are a lot of FBOs who'd just ignore the squawk. BTDT. One locally here used to take troubleshooting costs out of a CFI's pay if the problem couldn't be found.

There's been significant changes at that one, so hopefully that went away. Not a good Safety culture at all.

Ouch. As if there paycheck was big in the first place.

 

[Henning]

Not to sound stupid but does taking off and then reducing to cruise power count as a checklist? That and flaps up if used. I only use the checklist when on the ground, before takeoff and after landing. I cannot tell you what the list even says about climb,cruise,etc.

Take off, turn off boost pump,reduce rpm to 2475, trim mixture for 12.7 a side and check my speed and climb and add fuel from there up to peak EGT then back it down 10+* lop. This lets me climb 150 kts, 370-390 CHT WOT all the way up. If I am going to stay on the deck, I'll pull the throttles back to 25" MP and if I want to run faster than 165, I can turn up to full rpm 2675 quite safely reducing my 'red box" at the same time.