Brakes Off? What's it all about?
Gizajob
Thread Starter
Join Date: Jun 2003
Location: uk
Age: 49
Posts: 627
Likes: 0
Received 0 Likes
on
0 Posts
Brakes Off? What's it all about?
Idle discussion in the pub yesterday and we drew a blank - if any expert out there can help, we'd be very interested:
For most, if not all light aircraft, the first checklist item on the DW checks is 'Brakes off'. Questions are - why would you have the brakes on? Wouldn't 'Brakes - pressure check' be a more useful and appropriate item, since no one I know of ever puts the brakes on after take-off (save for the little dab to stop the wheels rolling before retraction)?
If anyone can throw any light on the reason for this item, we're all ears...
For most, if not all light aircraft, the first checklist item on the DW checks is 'Brakes off'. Questions are - why would you have the brakes on? Wouldn't 'Brakes - pressure check' be a more useful and appropriate item, since no one I know of ever puts the brakes on after take-off (save for the little dab to stop the wheels rolling before retraction)?
If anyone can throw any light on the reason for this item, we're all ears...
Join Date: Aug 2000
Location: Scotland
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
I was always taught "brakes set". Most of my flying is in a Chipmunk, which requires a couple of notches on the brake lever in order to give you differential braking. When landing with a crosswind, you need a small amount of differential braking to keep the aircraft straight during the landing run. You might sometimes also need brakes set for takeoff for the same reason - if there was no crosswind on the subsequent landing, then you would need to take the brakes off again.
Gizajob
Thread Starter
Join Date: Jun 2003
Location: uk
Age: 49
Posts: 627
Likes: 0
Received 0 Likes
on
0 Posts
Very interesting - we thought reasons may come from ways certain 'classic' aircraft were operated. 'Brakes set' is obviously a really important item for DHC pilots then, but I'm still puzzled as to why they include 'brakes off' for say a C152 if it doesn't apply - after all, they don't ask you to check for 3 greens...
Join Date: Aug 2000
Location: Scotland
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
It's all about teaching pilots generic techniques that they can use no matter what type of aircraft they are flying. I learned to fly in a PA28 so setting the brakes was not relevant, but I didn't have to learn a different check when converting to the Chipmunk. PPL students are also taught to point the controls into the wind, which makes no real difference unless the wind is really strong; in the Chipmunk, it's very difficult to taxi unless the stick in pointing into the wind.
Join Date: Mar 2000
Location: U.K.
Age: 46
Posts: 3,112
Likes: 0
Received 0 Likes
on
0 Posts
Brakes in the downwind check should be to check for pressure in the system first and then checking that the parking brake hasn't been set inadvertantly second. This can happen on certain types.
Gizajob
Thread Starter
Join Date: Jun 2003
Location: uk
Age: 49
Posts: 627
Likes: 0
Received 0 Likes
on
0 Posts
Understand that and agree - our discussion yesterday was more along the lines of - if 'brakes off' isn't meaningful, should 'brakes-pressure check' be there instead as something that might be useful? It would be in the same vein as the undercarriage call of 'fixed' or 'down and green' - slight risk of saying the wrong thing in the wrong aircraft but reflecting the type of system in general.
Can you elaborate on which types may suffer from inadvertant park brake selection? I am familiar with Robin (knob and umbrella handle type), Cessna and Piper systems and struggle to see how, assuming you released the brakes properly on take off (which I take it you might notice from performance), you could select brakes on at a later stage.
Can you elaborate on which types may suffer from inadvertant park brake selection? I am familiar with Robin (knob and umbrella handle type), Cessna and Piper systems and struggle to see how, assuming you released the brakes properly on take off (which I take it you might notice from performance), you could select brakes on at a later stage.
There's a yarn in the current issue of Todays Pilot which describes someone in a PA28 taking off with the brakes partially on, then landing and taxying in with the brakes still on using lots of power - so it would seem to be a worthwhile check, at least in PA28 and 172 types.
Join Date: Sep 2001
Location: UK
Posts: 255
Likes: 0
Received 0 Likes
on
0 Posts
Quote:
Can you elaborate on which types may suffer from inadvertant park brake selection? I am familiar with Robin (knob and umbrella handle type), Cessna and Piper systems and struggle to see how, assuming you released the brakes properly on take off (which I take it you might notice from performance), you could select brakes on at a later stage.
The reason why we do these things is the old airmanship adage 'don't assume, check'
Can you elaborate on which types may suffer from inadvertant park brake selection? I am familiar with Robin (knob and umbrella handle type), Cessna and Piper systems and struggle to see how, assuming you released the brakes properly on take off (which I take it you might notice from performance), you could select brakes on at a later stage.
The reason why we do these things is the old airmanship adage 'don't assume, check'
Join Date: Jun 2001
Location: England
Posts: 1,006
Likes: 0
Received 0 Likes
on
0 Posts
Isn't there an aircraft you have to set the brakes on for aerobatics and spin recovery. (something to do with more rudder authority). After such an exercise it would be useful to have a reminder put them off again.
I guess it also acts as as a reminder to the student to put their heels on the floor incase in their tense exitement they have allowed their feet to ride up.
Either way landing with brakes on is usually expensive.
Having said that don't some jets fitted with anti locking systems land with their brakes on for decreased stopping distance.
I guess it also acts as as a reminder to the student to put their heels on the floor incase in their tense exitement they have allowed their feet to ride up.
Either way landing with brakes on is usually expensive.
Having said that don't some jets fitted with anti locking systems land with their brakes on for decreased stopping distance.
Gizajob
Thread Starter
Join Date: Jun 2003
Location: uk
Age: 49
Posts: 627
Likes: 0
Received 0 Likes
on
0 Posts
You should all have been in the pub on Sunday - some new ideas we didn't think of coming up...
Totally with you on the 'don't assume-check' thing - we were also concerned with making sure the 'check' is of something useful! Very interested on the aerobat angle - anyone know which type that is?
Totally with you on the 'don't assume-check' thing - we were also concerned with making sure the 'check' is of something useful! Very interested on the aerobat angle - anyone know which type that is?
I have never seen a checklist that had brakes off as a prelanding check, I have always tought " brakes -- Pedals firm " as a quick squeeze on the pedal /brake handle in order to ensure the brakes are still there when you land. I once had a flight in a Seneca where the brakes worked fine on the ground but all the fluid leaked out in flight. I was more than a little surprised when I did a brake check and the pedals flopped to th floor
. I informed ATC and put the airplane down at the very beginning of the runway at min safe airspeed and it still took almost 6000 feet to stop
A final niggly point about the brakes -presure check call discussed in a earlier post. I believe the check calls should be what is actually checked. Since almost all light airplanes do not have a brake pressure guage you cannot check the brake pressure. Therefore the check should say what you are actually doing which is checking that the pedals are firm. The only exception I have encountered was a Nanchang CJ6 which had a brake airpressure guage directly showing the airpressure at the wheel brake bladders... and the Chipmunk of course with its goofy
system.
. I informed ATC and put the airplane down at the very beginning of the runway at min safe airspeed and it still took almost 6000 feet to stop A final niggly point about the brakes -presure check call discussed in a earlier post. I believe the check calls should be what is actually checked. Since almost all light airplanes do not have a brake pressure guage you cannot check the brake pressure. Therefore the check should say what you are actually doing which is checking that the pedals are firm. The only exception I have encountered was a Nanchang CJ6 which had a brake airpressure guage directly showing the airpressure at the wheel brake bladders... and the Chipmunk of course with its goofysystem.
Join Date: Aug 2002
Location: Lincs.
Posts: 157
Likes: 0
Received 0 Likes
on
0 Posts
A few years ago I flew a mates Grumman A A 5. This had a terrible habbit of both wheels freewheeling in flight, causing a horrible whine and vibration too, albeit not too much vibration. To stop this... The parking break was applied... Problem solved...
Pre landing checks were "Brakes Off!" for that very reason.
Hope this helps.. DP.
Pre landing checks were "Brakes Off!" for that very reason.
Hope this helps.. DP.
Join Date: Nov 2003
Location: notts
Posts: 636
Likes: 0
Received 0 Likes
on
0 Posts
brakes off
You apply brakes on a C150/152 by first pressing the pedals downwards with the feet. You then pull out a sprung toggle which, via the springs and attached chains, lift up clams (my word) which grip each brake master cylinders piston rod, both left and right. You release the brakes by pressing once more on the pedals and the clams fall away clear of the piston rods.
Should the toggle not return fully home then a tention is retained on the springs and chains. If in this condition the brakes are applied eigther deliberately whilst taxxing or inadvertently during flight then one or both brakes could become partially operative. The result on landing is obvious and most serious should just one brake be partially on.
The C150/152 brakes therefore, during the BUMPFH, should be checked for servicabilty by pressing with the feet but only after checking to ensure that the toggle is fully home.
I,m sure that we must all be agreed that the replies already posted show that checking the brakes ain't a bad idea. Re-invent the wheel if you dare!
Should the toggle not return fully home then a tention is retained on the springs and chains. If in this condition the brakes are applied eigther deliberately whilst taxxing or inadvertently during flight then one or both brakes could become partially operative. The result on landing is obvious and most serious should just one brake be partially on.
The C150/152 brakes therefore, during the BUMPFH, should be checked for servicabilty by pressing with the feet but only after checking to ensure that the toggle is fully home.
I,m sure that we must all be agreed that the replies already posted show that checking the brakes ain't a bad idea. Re-invent the wheel if you dare!
I am not sure how the parking brake in a C150 could be inadverantly applied in flight and if it was on during the takeoff, surely the pilot should have realized something was wrong. 
There certainly is not great amounts of thrust to overcome a dragging brake. I think checklists, particulary during high workload times like prelanding, should be as short as possible. I do not think it is worth while checking for something that is very unlikely to occur. Checking the brake pedals to ensure they are firm and thereby having reasonable certainty that the brakes are working does strike me as a worthwhile check. BTW I discourage the use of C150/152 style parking brakes because they do as you correctly point out , can jam on, and in any case it is hard on the disks if they are applied when the wheel is hot.
There certainly is not great amounts of thrust to overcome a dragging brake. I think checklists, particulary during high workload times like prelanding, should be as short as possible. I do not think it is worth while checking for something that is very unlikely to occur. Checking the brake pedals to ensure they are firm and thereby having reasonable certainty that the brakes are working does strike me as a worthwhile check. BTW I discourage the use of C150/152 style parking brakes because they do as you correctly point out , can jam on, and in any case it is hard on the disks if they are applied when the wheel is hot.
Join Date: Aug 2000
Location: Scotland
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Regarding 18Greens' query about types that require brakes to be set for spinning and aeros, to the best of my knowledge the rule is always to set the brakes off. Taking the Chipmunk again as an example: as you bring the brake lever back, you get progressively more braking as you deflect the rudder bar. Since you are now pushing against the hydraulic pressure, the rudder travel decreases. When the lever is fully back, you can't move the rudder at all!. This is clearly not desirable if recovering from a spin or trying to make coordinated manoeuvres during aerobatics.
Gizajob
Thread Starter
Join Date: Jun 2003
Location: uk
Age: 49
Posts: 627
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for all the response on this one - very interesting to hear all the different views and I certainly learnt something. I'll post what the guy I discussed this with says on the subject of C150 brakes - he's an ATPL and a licensed engineer, so I'm sure he'll have a take on it!
Join Date: Mar 2000
Location: U.K.
Age: 46
Posts: 3,112
Likes: 0
Received 0 Likes
on
0 Posts
I can't imagine putting on a C150 park brake inadvertantly. Since they are invariably useless it probably doesn't even matter that much!
The only a/c I've seen someone put on the parking brake during flight accidently, was in a Robin, but this was due to a complete brain dump on the part of the student.
Checking that there is pressure in the system is the main point in the brakes bit of the pre-landing checks.
The only a/c I've seen someone put on the parking brake during flight accidently, was in a Robin, but this was due to a complete brain dump on the part of the student.
Checking that there is pressure in the system is the main point in the brakes bit of the pre-landing checks.
Join Date: Aug 2002
Location: Lincs.
Posts: 157
Likes: 0
Received 0 Likes
on
0 Posts
Come on BP get real... Next you will be saying lets not check carb heat or similar cos its unlikely to happen... And we all know the common regularity of this! Particularly in the hot summer months!
I will always make sure the brakes off item are on the pre landing checks and I suggest that if the workload is too high for the pilot to manage to check brakes off, I would seriously question if the individual should be in command of any Aircraft, and their ability to fly in the first place.
Safety must come first, and this is definately a safety item.
DP
I will always make sure the brakes off item are on the pre landing checks and I suggest that if the workload is too high for the pilot to manage to check brakes off, I would seriously question if the individual should be in command of any Aircraft, and their ability to fly in the first place.
Safety must come first, and this is definately a safety item.
DP
Divergent Phugoid
While in the circuit I once had a wasp come out a C150 wing root airvent. Another time a student puked all over the instrument panel obscuring most of the instruments
. Because of those incidents I did not subsequently add to my prelanding checklist
Wing air vents -------- close
or
Puke Bag -------------- give to student
So why would I put something on the checklist that has NEVER in 5000 hrs, happened to me. I think you have to be carefull about invoking the " safety " word. Safety does not come from mindlessly following a printed list , it comes from fully understanding the relavance of each checklist item and always maintaining the correct priority of actions at any given time throughout the flight.
While in the circuit I once had a wasp come out a C150 wing root airvent. Another time a student puked all over the instrument panel obscuring most of the instruments
. Because of those incidents I did not subsequently add to my prelanding checklistWing air vents -------- close
or
Puke Bag -------------- give to student
So why would I put something on the checklist that has NEVER in 5000 hrs, happened to me. I think you have to be carefull about invoking the " safety " word. Safety does not come from mindlessly following a printed list , it comes from fully understanding the relavance of each checklist item and always maintaining the correct priority of actions at any given time throughout the flight.