Ask a Pilot anything....
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Yes most of the stopping is done by braking. Autobrake is used most of the time however frequently overiden to manual by pushing the top of the rudderpedals ( talking airbus 320/B737) to adjust the deceleration required to vacate the runway. The auto brake in these aircraft will give a set deceleration ie A330 LOW auto brake 1.7m/s squared. I believe the a380 has a 'brake to vacate' system so effectively the autobrake will adjust deceleration to vacate on a specific exit on the runway. Autobrake helps as it usually applies the braking more evenly especially in crosswind.
There's different levels of reverse thrust. Reverse Idle is almost always selected on landing. This effectively cancels out the forward thrust that is naturally produced by a jet engine even when it's operating at idle. A lot of airports prohibit the use of full reverse thrust except for safety requirements due to noise restriction so is rarely used. So if your runway performance calculation says you need it then you would use full reverse or if you have a technical defect where your stopping performance is decreased or you've landed and you don't feel the aircraft is slowing down as much as you would like. Reverse thrust is more effective at higher speed than lower speeds.
There's different levels of reverse thrust. Reverse Idle is almost always selected on landing. This effectively cancels out the forward thrust that is naturally produced by a jet engine even when it's operating at idle. A lot of airports prohibit the use of full reverse thrust except for safety requirements due to noise restriction so is rarely used. So if your runway performance calculation says you need it then you would use full reverse or if you have a technical defect where your stopping performance is decreased or you've landed and you don't feel the aircraft is slowing down as much as you would like. Reverse thrust is more effective at higher speed than lower speeds.
Cobnapint said:
Secondly, once on the ground at taxi speeds the rudder would become useless - how is the nose wheel operated for steering the thing back to the terminal?
Of course Harrier pilots could get into an interesting situation of being too slow for the rudder to work while still in the air.Dr Jekyll said:
Of course Harrier pilots could get into an interesting situation of being too slow for the rudder to work while still in the air.
Countdown said:
Didn’t they have puffer jets in the nose and tail for direction control at low speed?
They did indeed have Reaction Jets in the nose, tail and wingtips for control in the hover.What I think Dr Jekyll is getting at is the Harrier's instability in yaw in the hover.
It wasn't so much lack of rudder authority (there would be no rudder authority in the hover since there would be no airflow over the rudder with no forward motion) as something called Intake Momentum Drag.
If you recall the Harrier had a relatively huge pair of intakes (rather like 'Plug's Ears' for those as remember the Beano). Get any yaw on in the hover and the drag caused by the intakes would exacerbate the effect(s) of yaw.
For those as know, the 'Secondary Effect' of Yaw is Roll; the 'Tertiary Effect' of Yaw is Pitch.
The upshot being, yaw in the hover would be rapidly exacerbated by Intake Momentum Drag leading to a huge and rapid increase in opposite yaw, leading to a rapid roll into the direction of that yaw, with a conconmittant rapid pitch down and an associated rapid rate of descent (outside the bang seat limits).
You can guess the rest.
Cobnapint said:
A couple of landing questions, I'm aware of reverse thrust and how it is operated but apparently most of the slowing down is done by the brakes - how are these operated, is there a pedal....?
Secondly, once on the ground at taxi speeds the rudder would become useless - how is the nose wheel operated for steering the thing back to the terminal?
Everything I flew had toe brakes, ie you kept your heels on the rudder pedals and operated the brakes by pressing against the top of the pedals with your toes.Secondly, once on the ground at taxi speeds the rudder would become useless - how is the nose wheel operated for steering the thing back to the terminal?
In terms of reverse thrust, Hercules and Jetstream had reversing props so you could stop rather quickly without ever touching the brakes. Actually you could stop really quickly!
Nimrod had 'Thrust Deflectors' on the outboard engines only (ie it killed the 'idle thrust' but it wasn't thrust reverse so you relied on the wheelbrakes).
HS 125 had no reverse thrust but had a 'Lift Dump' system - on the landing roll out (with Land Flap applied) you would select Airbrake (thus killing any lift on the wing) and the Flaps would rotate to 73 degrees acting as 'Barn Doors'. The a/c would stop fairly quickly!
WRT to nosewheel steering all the above types had a small 'steering wheel' to the left of the Control Column or on the LHS console. During the landing roll you'd get on the nosewheel steering as the speed fell below 50 Kts.
Ginetta G15 Girl said:
Dr Jekyll said:
Of course Harrier pilots could get into an interesting situation of being too slow for the rudder to work while still in the air.
Countdown said:
Didn’t they have puffer jets in the nose and tail for direction control at low speed?
They did indeed have Reaction Jets in the nose, tail and wingtips for control in the hover.What I think Dr Jekyll is getting at is the Harrier's instability in yaw in the hover.
It wasn't so much lack of rudder authority (there would be no rudder authority in the hover since there would be no airflow over the rudder with no forward motion) as something called Intake Momentum Drag.
If you recall the Harrier had a relatively huge pair of intakes (rather like 'Plug's Ears' for those as remember the Beano). Get any yaw on in the hover and the drag caused by the intakes would exacerbate the effect(s) of yaw.
For those as know, the 'Secondary Effect' of Yaw is Roll; the 'Tertiary Effect' of Yaw is Pitch.
The upshot being, yaw in the hover would be rapidly exacerbated by Intake Momentum Drag leading to a huge and rapid increase in opposite yaw, leading to a rapid roll into the direction of that yaw, with a conconmittant rapid pitch down and an associated rapid rate of descent (outside the bang seat limits).
You can guess the rest.
I'm no Harrier pilot (obviously) but was recounting what John Farley (Harrier test Pilot told me) along with a couple of 'Bona Mates' (Harrier Jocks) who are good friends and who were on my BFTS.
Don't forget that Harrier had a serious anhedral wing which would increas the yaw/roll/pitch couple.
Don't forget that Harrier had a serious anhedral wing which would increas the yaw/roll/pitch couple.
Ginetta G15 Girl said:
I'm no Harrier pilot (obviously) but was recounting what John Farley (Harrier test Pilot told me) along with a couple of 'Bona Mates' (Harrier Jocks) who are good friends and who were on my BFTS.
Don't forget that Harrier had a serious anhedral wing which would increas the yaw/roll/pitch couple.
Oh god I'm not challenging it! Just find it really surprising. Cheers Don't forget that Harrier had a serious anhedral wing which would increas the yaw/roll/pitch couple.
VansDriver said:
Did the gyroscopic precession of the turbine not have any effect? I gather gyroscopic effects of jet engines can result in some pretty weird spin recovery techniques for small airlift?!
The Harrier engine has contra- rotating high pressure and low pressure shafts specifically to minimise the gyroscopic effect.Willy Nilly said:
Seriously though, you can probably imagine when a bunch of youngish people with a bit of cash and an expense account get shoved into close proximity to each other and then get sent off to far flung places with cheap (read free) booze and often no strings. In the days before I met my wife, I enjoyed every single minute of it! It's not as hedonistic as it once was though...
As a group Pilots and Cabin crew tend to be fairly outgoing types and when they are young, free and single (or just don't care about that whole not cheating thing) then stuff happens. We've all got tales of legendary room parties and streaking the hotel halls at some unearthly hour.
However, things have changed, companies have clamped down on some of the wilder aspects, liberating miniatures from the bars is not as easy as it once was, schedules have changed meaning less time on the ground down-route and simply the culture has "grown up" a bit. That's not to say that fun doesn't still happen, it's just a little more discrete than it used to be.
Mind you, I do have one tale of a night in a hotel in CDG with a bunch of Korean Cabin Crew. Dear god. I need to lie down after just thinking about it. I know I was very, very happy when we got the news that the loaders had gone on strike the next day and we were stuck for another 24hrs.
IforB said:
Mind you, I do have one tale of a night in a hotel in CDG with a bunch of Korean Cabin Crew. Dear god. I need to lie down after just thinking about it. I know I was very, very happy when we got the news that the loaders had gone on strike the next day and we were stuck for another 24hrs.
Thanks for giving us an idea at least of the goings on!The extract above leads me to my next question - there is the odd report on the news about pilots being arrested or disciplined for pitching up over the limit. How unusual is it for pilots, after a stopover of legendary proportions, to turn up for work feeling a bit...secondhand?
Europa1 said:
IforB said:
Mind you, I do have one tale of a night in a hotel in CDG with a bunch of Korean Cabin Crew. Dear god. I need to lie down after just thinking about it. I know I was very, very happy when we got the news that the loaders had gone on strike the next day and we were stuck for another 24hrs.
Thanks for giving us an idea at least of the goings on!The extract above leads me to my next question - there is the odd report on the news about pilots being arrested or disciplined for pitching up over the limit. How unusual is it for pilots, after a stopover of legendary proportions, to turn up for work feeling a bit...secondhand?
Nowadays, things are very different. Really. It just isn't acceptable anymore to turn up bleary eyed and wondering what day it is. When I first qualified there wasn't actually a blood alcohol limit specified and the rule was no "significant" amounts of alcohol in the 24hrs before flight, with an 8hr bottle to throttle rule saying no alcohol before flying.
This was old fashioned, open to abuse and I'll be blunt when I say I saw a lot of it and pushed it a few times myself. Nothing serious, but the mindset was different. I wouldn't dream of it now.= and would have no issue in hauling someone else up for doing it.
In ye olden days, then booze and flying was almost part and parcel of it. Just remember that a lot of pilots had come through the second world war and often had been what we'd term functioning alcoholics nowadays. To get in a Lancaster I think I'd have needed a few pints of Dutch courage personally and it sort of became ingrained. It wasn't open, but it was tolerated until it became a problem (IYSWIM.)
Now, drinking and flying is rightly frowned upon by all. I wish that it was dealt with a bit more decorum as used to be the way (pilots who stepped over the limit would be quietly dealt with by the company by going sick and being put through company provided drying out procedures before returning much of the time) but I suppose the publicity scares people into compliance.
WilliamWoollard said:
How much of the engines available power is used for a typical take off of a jet liner?
Depends - once you enter all the variables, weight, air pressure (pressure altitude), temp, runway length, runway condition and a few other bits into the FMS, it will give you an answer as to the flex/power used, so as to give the correct safety margin vs least engine wear. Recently took a flight where the take off was a bit concerning as the acceleration was comparable to that of a wheezy bus, and it has gone wrong a couple of times in the past - https://aviation-safety.net/database/record.php?id...
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