Tapping brakes on gear retract?

[EricJ]

13 minutes ago, N201MKTurbo said:

I'm a TI man, I never warmed up to the RPN thing. I can run one, but it just seems backwards.

It's way faster for complex stuff once you get used to it, but there's definitely a learning curve.   Once you're adapted, though, everything else is ruined. 

[Tim-37419]

3 pages in 9 hours. Call me impressed  

[MikeOH]

1 hour ago, N201MKTurbo said:

I'm a TI man, I never warmed up to the RPN thing. I can run one, but it just seems backwards.

Yeah, I had a TI-55 before the HP-15C came out.  Like @EricJ says, RPN is faster for more involved calcs; the stack concept is a great thing  Now, on the other hand, I can't run a 'regular' calculator; I try to put two numbers in and then press '+'

[dkkim73]

2 hours ago, 0TreeLemur said:

 

My reaction: 

 

[dkkim73]

1 hour ago, EricJ said:

It's way faster for complex stuff once you get used to it, but there's definitely a learning curve.   Once you're adapted, though, everything else is ruined. 

For blasting through real work in a lab or long physics academic tasks or projects, it was so much faster and more supple. 

Probably emblematic of how rote my quant work is these days that I only go aggressively digging every few months... I even bought a real HP12C once for some financial stuff but it falls flat on engineering. New modern 35S for general work and to teach my children, not quite the same heft all-in-all. 

The horizontal candybar form-factor/UX was killer even before the Nintendo era. 

Edited January 12 by dkkim73
Add 35S ref.

[GeeBee]

I tap mine. I got into the habit early in my career. Later when I flew jets I didn't have to worry about it as they brake automatically on retraction. Some time in my career I had a few planes with a brake "capped" meaning the hose was removed and there was no hydraulic power to the brake. The MEL said, to wait 5 minutes after takeoff before retracting the gear. I believed it was to prevent a spinning wheel come up in the well. 

Then one day, I was doing an acceptance test in Toulouse on an Airbus. We were informed one brake would be capped. I said, I'm not sure we can do an acceptance test due to the 5 minute requirement and it would not be a "normal takeoff profile" required by the test card. A discussion ensued and I was informed by Airbus engineer that the reason for the 5 minutes is due to the gyroscopic forces placed on the gear during retraction of a spinning wheel. Those forces are not forces normally encountered by the gear on the bearings, struts and trunnions. When you play with a toy gyroscope and place the axle horizontal, then try to "retract" you can see the forces are substantial. (90 degrees to the force applied)

 

[Joshua Blackh4t]

If I hear mine then I tap them. Just to make sure the noise stops and it isn't a sign of anything going wrong.

 

Also, I use a scientific calculator app. But I still have my old high school calculator for when I need to work with some figures written on my phone. 

[GeeBee]

In another "hmmm" some Boeing airplanes brake the nose wheel by placing "snubbers" in the nose wheel well. The snubber is a brake pad like material mounted to a spring like plate. When the nose wheel came up the tires would hit the snubbers and stop. An airline I worked for, in a cost cutting move removed the snubbers. Saves money right? Less wear on the tires, no snubbers to replace. Wrong! Because the snubber "trued the tire" by grinding on it every takeoff. Without the tire being snubbed it would always stop at the same heavy position which only got heavier without being trued then it would start to shimmy on landing.

[Shadrach]

Man’s age old question…”Should I tap that?”

[jetdriven]

8 hours ago, Immelman said:

That's an interesting thought on being kind to the wheel bearings on the mains. Hard to stop the nose gear though, but its being rotated back parallel to the axis of rotation so..... maybe a detour back to basic physics class is in order for that thought experiment!

FWIW in transports the brakes are typically applied automatically to stop MLG rotation. No brakes on the NLG, they're stopped by snubber pads in the wheel well which makes an interesting noise for a few seconds.

Landing the airplane in a crab is going to put more side load  on the bearings than any gyroscopic procession,  same thing with a hard landing. and in either  case, those parts are robust  enough. Has anybody ever heard of a wheel bearing failure from a hard landing or otherwise? I only see them get corrosion and get thrown out, but I’ve never seen one fail from  anything else. 

[Shadrach]

6 minutes ago, jetdriven said:

Landing the airplane in a crab is going to put more side load  on the bearings than any gyroscopic procession,  same thing with a hard landing. and in either  case, those parts are robust  enough. Has anybody ever heard of a wheel bearing failure from a hard landing or otherwise? I only see them get corrosion and get thrown out, but I’ve never seen one fail from  anything else. 

That’s why I always slip into the wind and make sure all of my landings are perfectly delicate touchdowns.

[Will.iam]

I would suspect that the older Moonies told you to tap the brakes in order to make raising the gear with the J-bar easier. Once we got electric motors, then tapping the brakes, didn’t really matter because you weren’t trying to lift the gear manually by hand anymore and the electric motor could take the extra gyroscopic load. Also our wheels are much smaller and spin much slower than airline gear. If you look closely on an airliner on takeoff you can see a puff of black smoke at the start of gear retraction. I think that is the brake dust and debris coming off the gear when the brakes are applied during the retraction sequence. 

[Will.iam]

I had a hp-48sx calculator in school you could program that thing to play space invaders! Loved to build algebraic equations, and have it solved for X or some other variable. It was cool. 

[amillet]

You all had it easy with your fancy calculators. Here’s what I had to use in my college physics classes 

[skykrawler]

9 hours ago, jetdriven said:

Has anybody ever heard of a wheel bearing failure from a hard landing or otherwise? I only see them get corrosion and get thrown out, but I’ve never seen one fail from  anything else. 

That's why we go through the annual ritual of removing wheels, clean/repack after 75 flight hours.

[BDPetersen]

Whew. This discussion makes me feel much better about myself. After 60+ years of flying I occasionally felt guilty about not having brake tapping on takeoff in my usual procedure. I think the Boeings handled that on their own, and something stuck in my brain that cautioned us against that in the DC-3 (maybe the DC-6) on the grounds it might spin the tire on the stopped wheel. Not sure that idea stands up to scrutiny, but it stuck with me.

Eliminating the gyroscopic forces makes perfect sense. At times I have had the presence of mind to do that before swinging the manual gear on my “C”, but I didn’t come up with a conclusion as to whether it made it any easier.

[N201MKTurbo]

It is hard to imagine the bearings would ever fail. They are the same bearings used on car wheels that will go hundreds of thousands of miles with no service. Being driven over rough roads which impart more stress than a hard landing, but the car does it constantly. 
 

Let’s say every flight takes 3 miles of rolling (YMMV) and your average flight is 1 hour and you fly 100 hours a year. That’s 300 miles per repacking. We all probably drive more than that every week.

[GeeBee]

9 hours ago, Will.iam said:

I would suspect that the older Moonies told you to tap the brakes in order to make raising the gear with the J-bar easier. Once we got electric motors, then tapping the brakes, didn’t really matter because you weren’t trying to lift the gear manually by hand anymore and the electric motor could take the extra gyroscopic load. Also our wheels are much smaller and spin much slower than airline gear. If you look closely on an airliner on takeoff you can see a puff of black smoke at the start of gear retraction. I think that is the brake dust and debris coming off the gear when the brakes are applied during the retraction sequence. 

Airliners don't have 1.5" axles either. That all said, the force is about 100 pounds on the axle mount for a 6x6.00 tire.

[Shadrach]

2 hours ago, N201MKTurbo said:

Let’s say every flight takes 3 miles of rolling (YMMV) and your average flight is 1 hour and you fly 100 hours a year. That’s 300 miles per repacking. We all probably drive more than that every week.

The most ridiculous make work item in GA is repacking wheel bearings every few hundred hours.

[0TreeLemur]

14 hours ago, N201MKTurbo said:

...never warmed up to the RPN thing. I can run one, but it just seems backwards.

Now that's funny!

[0TreeLemur]

14 hours ago, EricJ said:

It's way faster for complex stuff once you get used to it, but there's definitely a learning curve.   Once you're adapted, though, everything else is ruined. 

That's a really good way to put it.  When on occasion I have to use an algebraic calculator, I feel like a fast bicycle racer having to get on a Schwinn with training wheels...

[Will.iam]

1 hour ago, BDPetersen said:

Whew. This discussion makes me feel much better about myself. After 60+ years of flying I occasionally felt guilty about not having brake tapping on takeoff in my usual procedure. I think the Boeings handled that on their own, and something stuck in my brain that cautioned us against that in the DC-3 (maybe the DC-6) on the grounds it might spin the tire on the stopped wheel. Not sure that idea stands up to scrutiny, but it stuck with me.

Eliminating the gyroscopic forces makes perfect sense. At times I have had the presence of mind to do that before swinging the manual gear on my “C”, but I didn’t come up with a conclusion as to whether it made it any easier.

The reason i don't buy the tire spinning on the wheel is every time you land the tire gets spun up from 0 to landing speed as fast or faster than the brakes can spin them down from takeoff speed to 0. Have not seen any tires spun on the wheel from landing so i don’t expect to see any from applying the brakes after takeoff. 

[Pinecone]

21 hours ago, A64Pilot said:

Wheels are nothing, think about the prop. I quit spinning a tailwheel around quickly when I gave that a thought, yet apparently it hasn’t caused any harm. Some of our models had 117” props and if it was a Garret it was turning at high RPM. Image what an aerobatic airplanes prop and crank go through.

And some aerobatic guys turn their engines up over 3000 RPM.

I tap the brakes.  When my FBO did some work, they noticed that there was evidence of the wheel cover screws were hitting things in the wheel well.

The covers are off, but I figure it can't hurt.

[Pinecone]

18 hours ago, 1980Mooney said:

No doubt the diameter of a 6.00X6 6 ply is 16.8-17.5" when pumped up to 42 psi and laying on the ground.  But at normal pressure and under load the tire will deflect and the effective diameter (and radius) will be less.  Both Michelin and Goodyear state that the "Static Loaded Radius (Inches) At Rated Load" is 6.9 inches. (effective 13.8 inch diameter)

Except that when you rotate, you lower the load on the tires and they grow to the unloaded weight.

[Pinecone]

18 hours ago, MikeOH said:

HP-15C for the win!

(Still use mine daily)

HP-41CV for me.