18th May 2011, 08:22
permalink Post: 1370
I know we seem to be straying a little off topic, but having two engines at high power against brakes set to park and all wheels chocked is going to produce a lot less torque than say a sudden stop from 30 knots at RTOW.
[I am too lazy to attempt the sums !]
[I am too lazy to attempt the sums !]
18th May 2011, 09:44
permalink Post: 1371
Quote:
| .... brakes set to park and all wheels chocked |
4 years ago Spanner Turner came to my rescue on ground runs with -
Quote below is from the Maintenance Manual. (a 747 manual, but you get the picture).
C. Prepare for Engine Operation.
(1) Check that airplane is parked in clean area with wheels on areas
that are free of oil, grease, or other slippery substances.
(2) Make sure the wheel chocks are installed at the main landing gear
wheels and ground locks are installed.
(a) Do these steps if you will operate the engines for a high power
engine run.
1) Make sure that the forward wheel chock is six to twelve
inches in front of the tires.
NOTE: This will cause the thrust of the engine to be held
by the frictional force between the airplane tires and the
ground, and not the wheel chock. The wheel
chocks do not have the same frictional force as the
tires. If the tires touch the wheel chock, some of
the frictional force between the tires and the
ground is lost, and the airplane can skid. The
wheel chocks are only used to prevent the airplane
from rolling if the airplane brakes were
accidentally released before or after the engine run.
17th Sep 2011, 17:42
permalink Post: 1459
Philflies
,
M2dude is right, and IIRC there is already a description of this much earlier in the thread.
The background of the 3/4 tab is, that
... on most aircraft you can - at the start of the take-off - 'run up the engines against the brakes', check they all deliver full power, and release the brakes only then.
... on Concorde it was impossible to 'hold the aircraft on the brakes' while going to full t/o thrust including the reheat (not so much because of insufficient brakes as insufficient 'footprint' of the wheels, IMHO).
... so, full t/o thrust (including reheat) didn't occur until the aircraft had already started the take-off roll.
If, at that point, one of the four reheats didn't light (which did happen at times), you did not have an awful lot of time to decide on whether you could continue 'on three' or had to reject the take-off.
Rather than having to check your pre-flight take-off calculations in a sheaf of papers or rely on your memory of the briefing, that little Heath Robinson "3/4 tab" gadget told you instantly whether to RTO NOW, or whether you could continue the take-off.
Sorry to repeat an old story, but Philflies asked the question, and not everybody has read the entire thread.....
M2dude is right, and IIRC there is already a description of this much earlier in the thread.
The background of the 3/4 tab is, that
... on most aircraft you can - at the start of the take-off - 'run up the engines against the brakes', check they all deliver full power, and release the brakes only then.
... on Concorde it was impossible to 'hold the aircraft on the brakes' while going to full t/o thrust including the reheat (not so much because of insufficient brakes as insufficient 'footprint' of the wheels, IMHO).
... so, full t/o thrust (including reheat) didn't occur until the aircraft had already started the take-off roll.
If, at that point, one of the four reheats didn't light (which did happen at times), you did not have an awful lot of time to decide on whether you could continue 'on three' or had to reject the take-off.
Rather than having to check your pre-flight take-off calculations in a sheaf of papers or rely on your memory of the briefing, that little Heath Robinson "3/4 tab" gadget told you instantly whether to RTO NOW, or whether you could continue the take-off.
Sorry to repeat an old story, but Philflies asked the question, and not everybody has read the entire thread.....
16th Dec 2011, 20:50
permalink Post: 1528
And I think they were level at 60,000' and M2 in under 9 minutes from brakes off!
16th Dec 2011, 23:44
permalink Post: 1531
Quote:
|
Originally Posted by
Shaggy Sheep Driver
And I think they were level at 60,000' and M2 in under 9 minutes from brakes off!
|
CJ
8th Apr 2015, 20:40
permalink Post: 1856
Ruddman -
No autobrakes.
(And - with my pedant's hat on - no 'manual' brakes either. Pedal brakes, yes. I know that the 'manual brakes' has become an accepted term, but the nonsense of it just bugs me….)
Stopping distances were good; from a higher Vapp we stopped rather shorter than a 'classic' 747. Filton was tightish, Bournemouth was worse….
First gen carbon brakes did not like being 'feathered' so we used them pretty firmly on every landing. At Filton, Bournemouth, E Midlands etc. you'd put the pedals to the floor after nose wheel touchdown. Allegedly no more wear doing this than feathering them along a long runway.
Reverse was pretty effective - more so than a modern bypass engine. We idled the outboards at 100kts and the inboards at 75kts so they weren't in play for the whole landing (reverse is most effective at higher speeds anyway).
It was a good 'stopper'. Thankfully.
No autobrakes.
(And - with my pedant's hat on - no 'manual' brakes either. Pedal brakes, yes. I know that the 'manual brakes' has become an accepted term, but the nonsense of it just bugs me….)
Stopping distances were good; from a higher Vapp we stopped rather shorter than a 'classic' 747. Filton was tightish, Bournemouth was worse….
First gen carbon brakes did not like being 'feathered' so we used them pretty firmly on every landing. At Filton, Bournemouth, E Midlands etc. you'd put the pedals to the floor after nose wheel touchdown. Allegedly no more wear doing this than feathering them along a long runway.
Reverse was pretty effective - more so than a modern bypass engine. We idled the outboards at 100kts and the inboards at 75kts so they weren't in play for the whole landing (reverse is most effective at higher speeds anyway).
It was a good 'stopper'. Thankfully.
9th Apr 2015, 00:35
permalink Post: 1858
Great information Exwk.
Didn't the early prototypes have a braking parachute ?
Didn't the early prototypes have a braking parachute ?
12th Apr 2015, 16:36
permalink Post: 1867
@ Volume
Sorry for slight delay; I hadn't a clue and had to ask an old friend who was directly involved in Flight Test. This is his verbatim reply:
I think that is about as much as one could hope for after all this time
Sorry for slight delay; I hadn't a clue and had to ask an old friend who was directly involved in Flight Test. This is his verbatim reply:
Quote:
|
I remember the Concorde braking parachute quite well and as I recall the parachute door indicated open during the first flight of 002 although the chute functioned normally on landing. As I recall the parachute was used quite a bit in the early days even during the 1972 overseas “Sales Tour”. Remember the prototypes were operating well above their max landing weight because of the amount of test equipment on board. The parachutes were repacked by our own Safety Equipment people who were fully qualified on all the safety Equipment we used on Concorde and on the Canberra. I don’t recall ever having life problems with the parachutes. I imagine the total number number of deployments would not be that high. I think it would have been an on-condition item. I can’t see that the Concorde parachute would bear any relation to the Caravelle system. Concorde was a much heavier aircraft with higher landing speeds. I feel sure that Concorde had a specific new design. Having been on board several times when the chute was used I think the crew liked the initial deceleration which the chute provided . Although I do recall landing at Bombay in very bad weather when the parachute was deployed and immediately jettisoned since it was pulling the aircraft off line. |
I think that is about as much as one could hope for after all this time