"Positive Rate, Brakes"

[bigblockz8]

I have a habit formed by many of my CFIs. From day one I've been told to apply brakes once a positive rate is established. I've only flown fixed gear and thinking about it, this seems useless. Good habit down the road but for now, really? I was watching the video about (super) wide or straight in approaches taught by CFI's that wear uniforms and such, you know that rant. Most of my CFI's were at a 141 school or had their eyes set on a jet.

Is this truly needed or is this something that just wears down on a 172's brakes more than necessary? I got praised by a new CFI because I subconsciously did this, forgot the entire thing until he reminded me. Yes he wears three stripes...

So were you taught the same? What logic is behind this minus complex procedures? Why not pretend to put gear up while I'm at it? I already have to call speeds; "Takeoff power set,airspeed alive,40,Vr, rotate, positive rate, brakes," why not "gear up?"

I personally feel silly every time I takeoff

 

[jpower]

I think I'd feel silly too. I wasn't ever taught to call out any speeds except "airspeed alive." No tapping of the brakes either, though I suspect that has more to deal with retractable gear and not wanting the wheels spinning really fast when you retract them, but I could be wrong. I certainly don't see a problem with letting your wheels spin for a while in a 172, though.

 

[bigblockz8]

I think I'd feel silly too. I wasn't ever taught to call out any speeds except "airspeed alive." No tapping of the brakes either, though I suspect that has more to deal with retractable gear and not wanting the wheels spinning really fast when you retract them, but I could be wrong. I certainly don't see a problem with letting your wheels spin for a while in a 172, though.

I try to get away with airspeed alive and 55,vr, or rotate. I doubt that the drag caused by spinning wheels on a 172 is really that substantial but when I rode with other CFI/students I notice the same thing, brakes. Three different schools, same thing!

 

[GCA319]

Procedures aside..I'll likel be in a postion where I will be looking for a full-time CFI position very soon (I already teach a little here and there) and my main demand is to NOT work for a flight school that makes their instuctors wear Airline Pilot uniforms

 

[DaleB]

Huh. My instructors told me to keep my toes OFF the brakes when I'm not using them so I don't get used to resting my feet on the brakes, potentially flat spotting tires on touchdown. Never had one tell me to use them after takeoff.

 

[GCA319]

Huh. My instructors told me to keep my toes OFF the brakes when I'm not using them so I don't get used to resting my feet on the brakes, potentially flat spotting tires on touchdown. Never had one tell me to use them after takeoff.

I've seen it done, but it is not something I do/teach unless I'm in a retract. Different airplanes call for different procedures and one does not have to use standard airline call outs to safely fly a 150. The emphasis (in my opinion and the FAA's) needs to be on SRM.

 

[denverpilot]

Is this truly needed or is this something that just wears down on a 172's brakes more than necessary? I got praised by a new CFI because I subconsciously did this, forgot the entire thing until he reminded me. Yes he wears three stripes...

I picked up the habit during RG training and just continued it. The amount of braking force to stop a free-rotating tire on a Cessna isn't going to pre-maturely wear out a brake pad, that's for sure. You could stop it easily by hand (if you could reach it and had a glove on).

When I was flying the poorly maintained rental fleet, I would have killed for a brake pad on the out of balance nose gear. (Ours was getting out of balance last year, and our mechanic owns a tire balancer... awesome. Back to normal this year. I hate the beating the humans and avionics take from the standard Cessna nosegear vibration seen on almost every rental. Let's not even talk about worn out shimmy dampeners...)

So were you taught the same? What logic is behind this minus complex procedures? Why not pretend to put gear up while I'm at it? I already have to call speeds; "Takeoff power set,airspeed alive,40,Vr, rotate, positive rate, brakes," why not "gear up?"

I personally feel silly every time I takeoff

Why? GUMPS is taught for everyone, and we all joke, "Undercarriage, down and welded!".

That habit will save you someday if you move back and forth between retracts and non-retracts. "Undercarriage, oh... Crap!".

Not sucking the gear up at takeoff is just less likely, you can see and feel the performance degradation from them hanging out there. (And in high-wing Cessnas, the first time you look out the window you'll see the darn tire still sitting there.)

There's some aircraft types that you really shouldn't start retraction until you can afford a big hit in performance, like Cessnas with "wangle-dangle" gear on a hot day up here. As the tires turn side-on to the relative wind along the aircraft's longitudinal axis, you'll feel it. Lots of drag. Once the handle is thrown and they unlock, they tend to drop right to that worst-case drag angle too, until the pump catches up and shoves them into the tail.

Up here at this altitude I was taught to leave the gear alone in the venerable old underpowered 172RG until well clear of obstacles.

So building an instant "positive-rate-gear-up" all in one breath habit, wasn't a good idea. My callout is "no runway remaining, gear up" and if we're just barely clearing the trees at the departure end in an aircraft type that adds drag while the gear is in transit, I don't pull the handle yet.

So... Don't feel silly. You're not doing anything wrong, AFAIK.

 

[GCA319]

I picked up the habit during RG training and just continued it. The amount of braking force to stop a free-rotating tire on a Cessna isn't going to pre-maturely wear out a brake pad, that's for sure. You could stop it easily by hand (if you could reach it and had a glove on).

When I was flying the poorly maintained rental fleet, I would have killed for a brake pad on the out of balance nose gear. (Ours was getting out of balance last year, and our mechanic owns a tire balancer... awesome. Back to normal this year. I hate the beating the humans and avionics take from the standard Cessna nosegear vibration seen on almost every rental. Let's not even talk about worn out shimmy dampeners...)



Why? GUMPS is taught for everyone, and we all joke, "Undercarriage, down and welded!".

That habit will save you someday if you move back and forth between retracts and non-retracts. "Undercarriage, oh... Crap!".

Not sucking the gear up at takeoff is just less likely, you can see and feel the performance degradation from them hanging out there. (And in high-wing Cessnas, the first time you look out the window you'll see the darn tire still sitting there.)

There's some aircraft types that you really shouldn't start retraction until you can afford a big hit in performance, like Cessnas with "wangle-dangle" gear on a hot day up here. As the tires turn side-on to the relative wind along the aircraft's longitudinal axis, you'll feel it. Lots of drag. Once the handle is thrown and they unlock, they tend to drop right to that worst-case drag angle too, until the pump catches up and shoves them into the tail.

Up here at this altitude I was taught to leave the gear alone in the venerable old underpowered 172RG until well clear of obstacles.

So building an instant "positive-rate-gear-up" all in one breath habit, wasn't a good idea. My callout is "no runway remaining, gear up" and if we're just barely clearing the trees at the departure end in an aircraft type that adds drag while the gear is in transit, I don't pull the handle yet.

So... Don't feel silly. You're not doing anything wrong, AFAIK.

For single retracts, your call is the correct one. The whole "positive rate" thing only comes into play once you start flying something with two spinny things instead of one.

 

[denverpilot]

For single retracts, your call is the correct one. The whole "positive rate" thing only comes into play once you start flying something with two spinny things instead of one.

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.

 

[fgcason]

not wanting the wheels spinning really fast when you retract them

And the nose gear doesn't have a brake so it continues to spin.

Anyone ever watch the wheels after liftoff at least on a light single like a 172 or 182? The don't spin very long so using the brakes is kind of pointless. It's not like the wheels are starting to retract as soon as the squat switches say it's ok to retract, well, it might but you probably shouldn't retract the gear that soon anyway.


So, what is the justifiable reason for touching the brakes to stop the wheels after liftoff? OWT or justifiable behavior? Don't forget that the nosewheel doesn't have a brake so whateve the reason, it has to be for the mains only.

 

[bigblockz8]

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.

 

[Henning]

Tapping the brakes stops the flat spotted mains from shaking the plane. From landing one I was taught to call the gear even if welded. In 20+ years and 2500 hrs, over half retract I have not forgotten the gear, not even close. Do I still call positive rate on launch and gear check on landing? Yep.

 

[kgruber]

Because of the Kutta-Joukowski effect, spinning tires are providing lift in the wrong direction, down. So stopping the spinning will provide more lift.

Be careful with those big "Tundra tires" on a Super Cub. The rotational forces are so strong and the hubs are so small, that tapping the brakes can cause the tires to dismount from the wheels. This is a real problem and some bush pilots use screws to screw their big tires to the wheel.

The brakes are very powerful for this job. Press them gently, and spin them down slowly.

 

[flyingron]

Henning has it, Unless your tires are out of balance and annoying you with their rattling after takeoff, there's no need to tap the brakes.

The "gyroscopic precession" nonsense on the retracting gear has been pretty much disproven.

 

[jnmeade]

I learned to tap the C150 brakes on take-off to stop the shimmying caused because they were still spinning and badly out of balance. I tapped the brakes on my T210. I find that on my CTSW, it is still useful to stop the brakes after lift off and I do. I never tapped the brakes on twins or jets.
The OP brings up an interesting point. I find so often, in my own experience and with others, that the dreaded Law Of Primacy is always in effect. If you plan to fly bigger iron later on, it can be useful to learn right away the usual callouts (such as GUMPS). If you do not, you have to overcome your initial learning and start a new procedure. If you never will fly more complex airplanes, then of course you don't need to learn it. If the CFI knows s/he's going to big iron later on, maybe the CFI is the one getting the training.
If the complaint is that all these callouts make flying seem more complicated than it needs to be or should be, well, flying and airplane is not driving a car (for most of us). Maybe we accept some complication in the name of safety. If the complaint is that the procedure taught is inapplicable and will never be needed, then I guess one complains to the CFI and if he won't change then you can forget it when you move on.

 

[Captain]

I fly a plane that does not need the brakes hit when you retract the gear. In fact, I don't think I've ever flown one that does. The point of tapping the brakes is to not bring spinning things into the wheel well.

Well, I recently flew with a guy who constantly tapped the brakes on gear retraction. First leg out of the box I was flying and when I called, "gear up" I felt him pushing the brakes. I asked what the hell that was about and he said it was habit.

Well, he was right about the habit thing. He kept it up leg after leg and I kept telling him to stay off my f'ing rudder pedals.

My opinion, it's a poor habit. If your plane needs it then do it. Few do...at least none of the ones I've flown. (PA28R, PA44 , PA34, CL65, P180, B727)

 

[Captain]

Oh, and there's one point above I simply HAD to respond to:

The negative lift developed by spinning tires could easily be offset by trimming your fingernails before flight. My point is they have such a small cross section and are spinning so slow as to be inconsequential. That isn't a reason to tap the brakes IMO.




Edit to add the word "be".

 

[dtuuri]

As noted, it's for vibration (fixed gear). The nose wheel doesn't get out of balance much if it's held off on landing and lifted off early on takeoff.

But if taxiing through slush or water in the winter, don't tap. Let them spin off the water and air dry, so they aren't frozen on touchdown.

dtuuri

 

[Everskyward]

While there is something to be said for the Law of Primacy I don't think it's necessary to be doing crew-style callouts in a trainer. I had never done callouts until way down the road when I was actually going to fly an airplane where they were done. My first reaction was

But really, it didn't take me long to learn how to do them. We are, after all, supposed to be able to learn new things.

As far as tapping the brakes goes, I learned to do that on retractables, supposedly to stop the spinning of the mains before they went into the well. Then I started flying airplanes where that wasn't necessary so I don't do it any more.

If you are going to move from airplane to airplane you can't fall too much in love with a certain procedure or habit since what applies to one airplane may not apply to another.

 

[TMetzinger]

I use and teach a "positive rate" call, just as a reminder to start the tasks that begin shortly after the climb begins - pitch for the appropriate climb speed, and clean up the airplane.

Note that "shortly after" means a couple hundred feet - that may be only a few seconds in a jet but often it's twenty or more in a GA single. I smack students hands if they immediately go for the gear in a retract single just after rotation. There's only a few situations where that's appropriate.

 

[lr60plt]

In a single, if the wheels are causing a vibration ill tap the brakes...if not, i don't.

In larger jets, when you select gear up some hyd pressure is sent to the brakes to stop them from spinning. Its built into the design of the system.

I cant stand when flight instructors wear epaulets.

 

[lr60plt]

I smack students hands if they immediately go for the gear in a retract single just after rotation. There's only a few situations where that's appropriate.

I know of one event that took place at a nearby airport a few years ago. An instructor wanted to show off and suck the gear up right after rotation on a Piper Arrow, hold it in ground effect...etc etc.

After he pulled the gear up, the aircraft settled back down. The prop started striking the ground. He continued to accelerate and flew around the pattern after the prop strike and came in and landed. Lucky it didn't stop the engine to end as a gear-up....still obviously had a nice engine overhaul claim and a bruised ego.

 

[Fearless Tower]

Well, I recently flew with a guy who constantly tapped the brakes on gear retraction. First leg out of the box I was flying and when I called, "gear up" I felt him pushing the brakes. I asked what the hell that was about and he said it was habit.

Well, he was right about the habit thing. He kept it up leg after leg and I kept telling him to stay off my f'ing rudder pedals.

Problem with developing it has a habit is that it can really screw you up if you ever move on to bigger airplanes. You can actually shear the valve stems off if you tap the brakes before retraction on the B-25.




Sent from my iPad using Tapatalk HD

 

[TMetzinger]

I know of one event that took place at a nearby airport a few years ago. An instructor wanted to show off and suck the gear up right after rotation on a Piper Arrow, hold it in ground effect...etc etc.

After he pulled the gear up, the aircraft settled back down. The prop started striking the ground. He continued to accelerate and flew around the pattern after the prop strike and came in and landed. Lucky it didn't stop the engine to end as a gear-up....still obviously had a nice engine overhaul claim and a bruised ego.

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.

 

[jnmeade]

While there is something to be said for the Law of Primacy I don't think it's necessary to be doing crew-style callouts in a trainer. I had never done callouts until way down the road when I was actually going to fly an airplane where they were done. My first reaction was

But really, it didn't take me long to learn how to do them. We are, after all, supposed to be able to learn new things.

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. We so seldom train cross country that when we do it's an event to do checklists and otherwise we ignore them As a result, after the pilot is done with training and actually does a lot of cross country flying, he has no ingrained habit to turn to a checklist. When he's in a team envirionment in 135 or 121, then that is different - he's in a different envirionment.
Anyway, I guess I get on a soap box about this and because of it I'm not too much against teaching reasonable call outs.
One aspect of the callouts is it can help, in my opinion, focus and keep one's attention on what one is doing. Again, I see many private pilots who,after they start on their own, treat the plane like the family car and drop their discipline and structure from flying. So, they'd don't brief a departure and when the engine quits at 400 feet instead of taking immediate action they take a pause to try to figure it out.
Like the old Indian said, what you see depends on where you stand and that is my perspective on topic. Sorry to ramble on and on.

 

[Fearless Tower]

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.

Dang.....I thought only Cape Air did that!

On a more serious note, I am amazed that someone would out that much faith in the switch.

We just had someone collapse the nose wheel on he club Duchess at the tie down. For some reason, they raised the gear lever and the airspeed limit switch failed to perform as advertised.

Sent from my iPad using Tapatalk HD

 

[fgcason]

Because of the Kutta-Joukowski effect, spinning tires are providing lift in the wrong direction, down. So stopping the spinning will provide more lift.

That's right up there with the whole gyroscopic force argument about it keeping the plane from turning. Yes the force exists however also, yes, it's so completely trivial to the point that it's totally overwhelmed by everything else.

The brakes are very powerful for this job. Press them gently, and spin them down slowly.

Have you ever used a brake on a tire, which is not in contact with the ground, that was spinning to slow it to a stop? No matter how gentle you are, it goes like this: spin, touchstop. Maybe it works on the tires of something like an AN225 but not on a CE150..but then again, the AN225 has brakes big enough to stop those tires too so it's probably the same.

 

[Palmpilot]

Not sucking the gear up at takeoff is just less likely, you can see and feel the performance degradation from them hanging out there. (And in high-wing Cessnas, the first time you look out the window you'll see the darn tire still sitting there.)

Reminds me of the time I climbed 7000 feet with the gear down in a Cutlass. I kept thinking, "Why is this thing climbing so poorly? I thought clouds were supposed to have updrafts in them!"

 

[kgruber]

I brought up the Kutta-Joukowski effect as a curiosity, just to mention spinning wheels are not doing you any good. You guys need to put a little sugar in your coffee this morning.

I've flown for 47 years and am typed in 4 jet series. I've never "tapped" the brakes even once. I don't remember which type it is but in the wheelwell there are brake pads that contact the tire during the last phase of retraction. Probably most wheelwells have them.

Complete waste of time.

 

[Palmpilot]

And the nose gear doesn't have a brake so it continues to spin.

Anyone ever watch the wheels after liftoff at least on a light single like a 172 or 182? The don't spin very long so using the brakes is kind of pointless. It's not like the wheels are starting to retract as soon as the squat switches say it's ok to retract, well, it might but you probably shouldn't retract the gear that soon anyway.


So, what is the justifiable reason for touching the brakes to stop the wheels after liftoff? OWT or justifiable behavior?

One reason for doing it in a 172RG is that the POH says to.

As for the justification, here's what the 1981 POH says about that:

"Centrifugal force caused by the rapidly-spinning wheel expands the diameter of the tire. If there is an accumulation of mud or ice in the wheel wells, the rotating wheel may rub as it is retracted into the well.​

So maybe the bit about mud or ice is the reason. I wouldn't expect them to design it so that it rubbed when the wheel wells were clean.

Don't forget that the nosewheel doesn't have a brake so whateve the reason, it has to be for the mains only.

Maybe the nosewheel compartment has more clearance.

 

[fgcason]

I brought up the Kutta-Joukowski effect as a curiosity, just to mention spinning wheels are not doing you any good.

The spinning wheels aren't really hurting anything either. You most likely lose considerably more lift than that from old rough paint on the wings than the wheels spinning.

 

[dtuuri]

You can actually shear the valve stems off if you tap the brakes before retraction on the B-25.

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

dtuuri

 

[Captain]

I will say this about callouts, often times they spur the mind into action.

I've seen many guys in the sim completely make an abortion out of a normal missed approach. But if the guys can get just the first phrase out ("missed approach, set max power flaps mid") then that cues the next guy to say, "positive rate" and that cues the first guy, "gear up" and on and on.

Flying in a crew is sorta like a play. The characters need to know their lines and if someone screws up and misses a line then the whole production can fall apart.

 

[Captain]

The spinning wheels aren't really hurting anything either. You most likely lose considerably more lift than that from old rough paint on the wings than the wheels spinning.

I think my example in post #17 of the lift loss being not enough to cover the weight of finger nail clippings is closer to the mark than rough paint.

Rough paint actualy has an effect that is measurable.

 

[Sac Arrow]

I don't tap the brakes when I fly retracts either. But I was taught to originally, though.

 

[Fearless Tower]

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

dtuuri

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.

 

[dtuuri]

I will say this about callouts, often times they spur the mind into action.

Or just the mouth into action before looking to confirm what they say.

Flying in a crew is sorta like a play. The characters need to know their lines and if someone screws up and misses a line then the whole production can fall apart.

How true. So, the best way I've found is to make callouts the responsibility of the non-primary caller too, after it's obviously been forgotten, or to repeat it at the appropriate time if it was uttered by the correct party, but too early. Like this, "NOW we have positive rate, gear up!"

dtuuri

 

[Henning]

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.

Dude, I watched a guy in a Navajo do that and say "watch how slick this is..." "Cool, lets see..."

 

[Palmpilot]

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

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?"

 

[dtuuri]

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 not an engineer, but to me it seems like the reason the wheel stops instantly, even if the tire doesn't slip, is because the total energy involved is miniscule compared to the momentum of the whole aircraft at touchdown. If the tire is going to slip on the rim, the shearing force would seem to be much, much greater on landing.

Perhaps somebody can explain it better if what you say is true?

dtuuri