How do you brake after landing ?
A smooth landing – a.k.a. “kiss landing”, don’t ask – is always good and rewarding. But it’s not the end. A safe aircraft is a parked aircraft. Between landing and parking comes the deceleration and taxiing phases. Taxiing can be risky, but this is not my point today. I’m much more interested in the way you slow down after landing. Not the classical debate about aerodynamical versus mechanical braking. All pilots learn to land with minimal speed and to reduce speed using as much aerodynamical braking before touchdown. What I’d really like to know is how you slow down after touchdown, using the brakes.
Why am I so interested in such a specific phase of flight ? Because I was taught different techniques by different instructors. Except for the seldom cases where no braking is required – very low landing speed and super-long runway – pilots are organized in two categories: the continuous brakers and the pumpers. In the beginning, I was a continuous braker. Then I met an instructor who tried to convert me into a pumper.
If you missed it, continuous braking means making constant use of brakes after landing until speed is sufficiently low. Pumpers prefer to increase braking pressure after landing, then reduce it, and increase it again. They pump on the brakes. Pumping requires an increased workload, but pilot brains are not that small… most of time. Because aircraft brakes can be controlled separately on each side, pumping increases the risk of directional control problems. Not that all pumpers drive like if they were drunk. It’s not that easy to drive with toe brakes anyway.
When I met my “pumper” instructor he told me about the reason why pumping is good: it reduces brakes temperature. As he’s also a jet pilot with immense flying experience, I could not simply turn the argument down. Does it apply to light aircraft as well ? The kinteic energy from a 1.5 tons aircraft rolling at 70 knots is much less than what the brakes of a light jet landing at 120 knots have to dissipate. Widebody airliners have even more energy to dissipate, and they get really really hot after landing. The picture below show the brakes of a British Aerospace Avroliner and the cooling system.
I checked the aircraft flight manual of the DA40 to see if one or the other technique is recommended by Diamond. I don’t know if this is a result of our hyper-reglemented world where no-one wants to take any risk, but what I found in the AFM was quite disappointing… The after-landing check-list mentions: BRAKES…..AS REQUIRED.
Which technique were you taught ? Which do you use now ? Do you use the same for all aircraft types ? I know that a handful of instructors read this blog (hi Paul, Jason, Max, and co…), and I’d really like a reaction from you guys… but also from any pilot.
12 Comments, Comment or Ping
Jason Miller
I’ve never heard of pumping the brakes on an aircraft – I just pull full aft elevator to maximize “air braking” and then put even pressure on the brakes the stop – without trying to make the first taxiway (unless required).
I don’t know about the less-heat argument. Certainly the heat is reduced when you let off the brakes, but to stop in the same distance with the pumping method you’d have to get on the brakes harder – meaning more heat and increased chance of locking the brakes. If you want to stop in the same distance, I would not think one method would be cooler than the other.
Jan 7th, 2009
Pat
I usually don’t use the brakes (800m grass runway and tail-dragger).
On short runways I brake continuously.
I only have one common brake lever for the 2 brakes and pumping would introduce instability. Decelerating a tail-dragger after landing on a short concrete runway with cross-wind is something that keeps me busy enough!
Jan 7th, 2009
Wayne Conrad
Beats me, and I don’t have a technique (not a pilot, as you may recall). But you may find this interesting. Here’s an accident report where the investigators cite pumping the brakes as a contributing factor:
http://www.tsb.gc.ca/eng/rapports-reports/aviation/1994/a94a0124/a94a0124.asp
”1.9.2 Braking Technique
”The flight crew were using a braking technique of brake on-off-on (pumping the brakes) after aircraft touchdown. An alternative braking technique would have been to apply the brakes after touchdown and maintain positive brake pressure until the aircraft had come to a stop. The latter technique provides a shorter landing distance. Also, the brake system, due to a higher constant brake pressure, could absorb more heat before the brake fluid would boil.
”The flight crew believed that their braking technique resulted in less wear and longer life to the aircraft brake system components. This technique was an accepted practice used by some of the operator’s pilots.
”The operator did not have a Standard Operating Procedure (SOP) manual for this aircraft.”
The report does not address whether or not the pilots were correct in their belief that pumping results in lower overall brake temperatures. But the investigators seem to believe that there are other costs to the pumping technique: longer landing distance, and the possibility of boiling the brake fluid sooner when the brakes are at an extremely high heat. They say so in 2.2:
”Had the PF maintained brake application rather than use the on-off-on braking technique, the increased brake pressure might have prevented the brake fluid from reaching the boiling point.”
On a longer field, or if the brakes had not been hot, one might suppose that things would probably have been fine. As with all accidents, the holes in the Swiss cheese had to line up. And, who knows. It was a short field and the brakes were very hot. Perhaps even steady braking would not have saved the day for those pilots.
Jan 8th, 2009
SEQU
I don´t know about your instructor, but i´ve never, ever seen pumping or anyone else pump for that matter where I fly. The company I fly for operates both Boeing and Airbus heavy jets, and neither one of the SOP includes pumping the brakes during landing. It´s Boeing and Airbus SOP.
Look at it this way, if any manufacturer (Boeing, Airbus, Gulfstream, Embraer, Bombardier, etc) thought that pumping were the way to do it, they would design their Autobrake systems to do that. I´m 99.99% certain that no design in operation is set up this way. 100% for the airplane I fly – B767, do you see what I mean?
In terms of heating your brakes, yes, it is a fact the heavier the aircraft, the more energy is absorbed by the braking system thus producing undesired heat, but and the big but, is what is the problem with the heat!!! In airliners, it limits the turnaround for the next flight usually, so some have Brake Fans installed, but for your operation, where usually you land don´t take off for another day (or week), there is no problem in letting the brakes warm up a little!!!
Don´t pump i say!!! A nice, elegant, smooth brake application will make you look and feel like a more professional pilot, that thinks about safety,the aircraft and the passengers´ comfort!!!
Happy Braking!!!
SEQU
Jan 8th, 2009
Julien
I do not think the brake temperature argument applies to GA aircrafts. To understand that, let’s compare GA aircrafts and cars.
Your typical Cessna or Piper is about the same weight and uses similar brake pads and discs as your average car. In addition, touchdown speed is similar to cruising speed for the average car.
True, car brakes can rise in temperature to the point of becoming ineffective if you break down continuously over several minutes. This is the case if you go down a mountain in 4th gear and only use the brakes to dissipate energy instead of shifting to a lower gear. But that’s much longer than the average deceleration on a runway and, most importantly, downhill.
So I doubt GA airplane brakes will ever get as warm as car brakes. Even with reduced braking capability, stopping a 172 taxiing at near human walking speed is different from stopping a car going down a mountain.
Pumping is what was taught to car drivers in the days before ABS because it is proven to prevent brake locking. That’s maybe why the myth still exists that pumping is better. If GA airplanes came fitted with ABS systems, there would be no debate between pumping and continuous braking.
By the way, did you know that the anti-lock braking system was invented by a Frenchman in 1929 for use in airplanes, not cars? 80 years later it would be nice is GA manufacturers took his invention onboard.
I posted a story a while ago illustrating what happens when one suddenly jumps on the brakes in a 172… Tires blow up long before brake pads combust
Jan 8th, 2009
Forrest
I teach my students to use full aft elevator until they get down to about 35-40 kts (in a Piper Warrior) and then smoothly apply even pressure on the brakes. Pumping the brakes in a light aircraft could definitely lead to a potential loss of directional control. I have heard of people being a little nervous about having the brakes overheat in a retractable gear aircraft, since the brakes get tucked right up next to the fuel tanks in many of them. This is really only an issue if you are doing pattern work, and even then it’s likely that only a brake fire would cause a problem.
Jan 8th, 2009
Sanjeev Bhadresa
Another vote for smooth braking. I must admit that I’ve not come across the “pumping method” and am not sure I would recommend it. As has been mentioned previously, there is a risk of directional control loss.
Jan 9th, 2009
Ron Amundson
I can think of perhaps a few unique situations and AC where pumping may be in order, but for 99% of the time, just applying the brakes as needed is all one needs to do. Some possibilities where pumping may be beneficial include specific brake systems on older aircraft, hydroplaning on some surfaces, albeit for GA and most textured runways a non issue, adverse weather, ie lots of slush, where periodic application can reduce the potential for freezeups etc. (a most unfun situation btw)
I think what happens is, pilots get themselves into the 0.001% situations, get freaked out, and then make up their own SOP to prevent that 0.001% deal, without considering the wider aspects. Then through hanger flying etc, the SOP propagates itself.
I’ve worked for a number of flight schools over the years, and have seen that played out over and over on a multitude of issues. Granted, for the most part, unlike this braking one, odd SOP’s do not impact safety, and I’ve even taught company techniques I personally was at odds with (provided they did not have an adverse safety impact), but shared with students alternative methods just so they were aware of them company permitting etc.
Jan 9th, 2009
Nick P
I’d say that pumping (hard) is also recommended for cars or trucks… Because it maximizes the pads’ efficiency by giving then time to dissipate caloric energy, I therefore guess that this would apply to large a/c that pack lots of kinetic energy either because they land fast or because they’re heavy.
Anecdotally, I have this strange reflex of braking after landing, which my CFI just hates and yelled at me for a couple of days ago. Pumping or continuous, I don’t think he would care…
Aug 8th, 2009
Vincent
@Nick: if you find that braking after landing is “strange” you probably never operated on short enough runways
Aug 8th, 2009
Nick P
No I haven’t yet, although we have a secondary very narrow 3000′ but practice on the 5700′. It’s just the “reflex” part that p**** him off. Can’t explain it myself. It just feels like the thing to do…
Aug 8th, 2009
Vincent
@Nick: the grass runway in Geneva (LSGG) has approximately 1700 feet landing distance available. Braking after landing until speed is controlled is a must.
Aug 8th, 2009
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