Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
How Do Planes Taxi Exactly?  
User currently offlineCaptainJon From , joined Dec 1969, posts, RR:
Posted (7 years 6 months 5 days 4 hours ago) and read 32767 times:

This maybe a dumb question, but I've always wondered how does a plane taxi? I mean, what causes it to move on the ground? For example, on a jet, do the turbofans cause the aircraft to move? Or do they simply generating electricity like how an electrical generating turbine would and the plane moves forward?

I imagine props are similar?

What confuses me is, when the plane is sitting parked, I often hear the engines revving up, to a rather powerful level that the parking breaks seem it shouldn't keep that plane parked. (Usually this seems to happen after pushback and the captain is going through the pre-flight check list).

Okay I hope I didn't confuse anyone, because I think I confused myself.

42 replies: All unread, showing first 25:
 
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4022 posts, RR: 33
Reply 1, posted (7 years 6 months 5 days 1 hour ago) and read 32767 times:

Yes, at present all aircraft use engine thrust to taxi. The parking brakes will keep an aircraft stationary up to nearly take off power.
A system of electric motor taxying has been developed, and you will see it on new aircraft soon. Delta has signed up for a system on their new B737s.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 2, posted (7 years 6 months 4 days 21 hours ago) and read 32767 times:

Quoting CaptainJon (Thread starter):

What confuses me is, when the plane is sitting parked, I often hear the engines revving up, to a rather powerful level that the parking breaks seem it shouldn't keep that plane parked.

The brakes (note spelling) can hold the aircraft even if the engines are almost at full thrust. They are viciously powerful.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineSP90 From United States of America, joined May 2006, 388 posts, RR: 0
Reply 3, posted (7 years 6 months 4 days 20 hours ago) and read 32767 times:

Quoting TristarSteve (Reply 1):
A system of electric motor taxying has been developed, and you will see it on new aircraft soon. Delta has signed up for a system on their new B737s

Indeed. Check out this prototype by Boeing.

767 Nose Wheel Electric Drive

I wonder how well it will work in wet/icy conditions. Would they still require a tug for pushback and engine power to taxi? Maybe an advance traction control would limit wheel slippage enough for it to work no matter the surface conditions.


User currently offlineInnocuousFox From United States of America, joined Dec 2003, 2805 posts, RR: 14
Reply 4, posted (7 years 6 months 4 days 20 hours ago) and read 32767 times:

In a manner of speaking, taxiing is a failed attempt at taking off. Big grin


Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
User currently offlinePizzaandplanes From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 6 months 4 days 19 hours ago) and read 32767 times:

So, what brakes do pilots use on landing- parking or emergency brakes?

Or is mostly thrust reversers?


User currently offlineMarquis From Germany, joined Sep 2005, 274 posts, RR: 1
Reply 6, posted (7 years 6 months 4 days 18 hours ago) and read 32767 times:

Quoting Pizzaandplanes (Reply 5):
So, what brakes do pilots use on landing- parking or emergency brakes?

Or is mostly thrust reversers?

They use neither of the first two ones you mentioned for landing. They simply apply the wheel brakes by pushing the upper tip of their rudder pedals, very similar to that in car. They can also select a certain degree of constant deceleration via the auto brakes switch. The A380 for example incorporates an automated system, by which you can preselect a certain turn-off from the runway and the system will apply brake force according to the pilot's desired exit.

Thrust reversers by contrast only assist the wheel brakes in order to lower their wear. Some jet engined aircraft are not even equipped with thrust reversers as a safe landing roll can be perfectly conducted with wheel brakes only.

[Edited 2007-04-21 18:56:33]


Riding the radials...
User currently offlineGoldenshield From United States of America, joined Jan 2001, 6070 posts, RR: 14
Reply 7, posted (7 years 6 months 4 days 17 hours ago) and read 32767 times:

Quoting Marquis (Reply 6):
Thrust reversers by contrast only assist the wheel brakes in order to lower their wear. Some jet engined aircraft are not even equipped with thrust reversers as a safe landing roll can be perfectly conducted with wheel brakes only.

To add to this: when an aircraft is decelerating, thrust reversers assist the brakes in slowing the aircraft, with the brakes being the primary way to slow the aircraft down.

An analogy to this is that of a car with a manual transmission: when you are approaching a stop light, you would use the brakes to slow you down, but if you incorporate compression braking (downshifting the transmission) into the equation, you can either: 1) save your brakes a lot of wear, by reducing the pressure and/or how long they are used, or 2) increase your deceleration rate by using compression braking on top of normal braking.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineGQfluffy From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 6 months 4 days 17 hours ago) and read 32767 times:

Quoting Goldenshield (Reply 7):
An analogy to this is that of a car with a manual transmission: when you are approaching a stop light, you would use the brakes to slow you down, but if you incorporate compression braking (downshifting the transmission) into the equation, you can either: 1) save your brakes a lot of wear, by reducing the pressure and/or how long they are used, or 2) increase your deceleration rate by using compression braking on top of normal braking.

And 3) Eat alot of gas. I did this for a while in my Taurus SHO. After a month or so of comparing gas milage, I was averaging 3-4 mpg less each tank... YMMV


User currently offlineCaptainJon From , joined Dec 1969, posts, RR:
Reply 9, posted (7 years 6 months 4 days 17 hours ago) and read 32767 times:

Quoting Starlionblue (Reply 2):
The brakes (note spelling) can hold the aircraft even if the engines are almost at full thrust. They are viciously powerful.

Oops! But thanks for the answer. And to everyone else. I learned something new!


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 10, posted (7 years 6 months 4 days 16 hours ago) and read 32767 times:

Quoting GQfluffy (Reply 8):
And 3) Eat alot of gas. I did this for a while in my Taurus SHO. After a month or so of comparing gas milage, I was averaging 3-4 mpg less each tank... YMMV

I don't understand what happened to you here. On pretty much any modern car, the electronics will cut fuel flow to idle when using engine braking. So even if you are engine braking your gas consumption at that point is the same as idle.

Oh wait. You have a Taurus (sorry couldn't resist)

[Edited 2007-04-21 20:11:27]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDoug_Or From United States of America, joined Mar 2000, 3421 posts, RR: 3
Reply 11, posted (7 years 6 months 4 days 16 hours ago) and read 32767 times:

Quoting Goldenshield (Reply 7):
...with the brakes being the primary way to slow the aircraft down.

For performance calculations, yes, however at least in practice on the CRJ, brakes are usually only engaged as reverse thrust is set to idle (below 75 knots). On the Dash it was similar- we slowed via beta, and used wheel braking briefly right before making the turnoff. Both were as per company procedures.



When in doubt, one B pump off
User currently offlineGoldenshield From United States of America, joined Jan 2001, 6070 posts, RR: 14
Reply 12, posted (7 years 6 months 4 days 16 hours ago) and read 32767 times:

Quoting Doug_Or (Reply 11):
For performance calculations, yes, however at least in practice on the CRJ, brakes are usually only engaged as reverse thrust is set to idle (below 75 knots).

There are always exceptions to the rule. I remember reading something about that in regards to loss of airflow to the rudder on aircraft of that configuration; however, is that a -200, or -7/900 we're talking about? At tight airports (BUR, SNA,) I would figure that policy could lead to possible 'issues.'



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 13, posted (7 years 6 months 4 days 16 hours ago) and read 32767 times:

Quoting Starlionblue (Reply 10):
I don't understand what happened to you here. On pretty much any modern car, the electronics will cut fuel flow to idle when using engine braking.

Yes indeed. Note also that in the case of idle, the fuel consumption will look like < 0. Of course that's physically impossible. However;

Quoting Starlionblue (Reply 10):
So even if you are engine braking your gas consumption at that point is the same as idle.

Yes sir.

Also, most injection engines will pre-charge the rail, and return it to the tank if it's not used. Hence the less-than-zero usage. Really GOOD engines, (like two of mine) will look at your driving style and precharge the rail accordingly. If you trick it, it does the return in bulk. This can be really odd when you see a good 1/4 tank disappear then come back again...



Todos mis dominós son totalmente pegajosos
User currently offlineInnocuousFox From United States of America, joined Dec 2003, 2805 posts, RR: 14
Reply 14, posted (7 years 6 months 4 days 15 hours ago) and read 32767 times:

Quoting Goldenshield (Reply 7):
An analogy to this is that of a car with a manual transmission: when you are approaching a stop light, you would use the brakes to slow you down, but if you incorporate compression braking (downshifting the transmission) into the equation,

Hehe... now we will see signs along the runway that say "no Jake Braking"!




Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 15, posted (7 years 6 months 4 days 14 hours ago) and read 32767 times:

Quoting InnocuousFox (Reply 14):
Hehe... now we will see signs along the runway that say "no Jake Braking"!

LOL Well the wheels aren't (directly) braked by the engines, so I guess the equivalent would be "No reverse thrust".

Isn't that the case already? ISTR that Palm 90 reversed from the gates under her own power and I have read here that some aircraft with rear-mounted engines still do so...



Todos mis dominós son totalmente pegajosos
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4022 posts, RR: 33
Reply 16, posted (7 years 6 months 4 days 13 hours ago) and read 32767 times:

Quoting InnocuousFox (Reply 14):
that say "no Jake Braking"!

OK I give up. Whats a jake when you use the brakes?


User currently offlineInnocuousFox From United States of America, joined Dec 2003, 2805 posts, RR: 14
Reply 17, posted (7 years 6 months 4 days 13 hours ago) and read 32767 times:

Jake Braking is the technique mentioned before of downshifting to use the high engine revs to slow down a truck. It makes quite a racket so many communities prohibit it at night... or entirely. I was making a joke on the analogy in Reply 7.


Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3702 posts, RR: 34
Reply 18, posted (7 years 6 months 4 days 11 hours ago) and read 32767 times:
Support Airliners.net - become a First Class Member!

Quoting Starlionblue (Reply 2):
The brakes (note spelling) can hold the aircraft even if the engines are almost at full thrust.

Not on the A320 series. If you are at full power on those and you do not want to move E.g. maint grnd run, you have to use the toe brakes to apply full braking pressue to prevent you from moving


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 19, posted (7 years 6 months 4 days 11 hours ago) and read 32767 times:

Quoting VC-10 (Reply 18):
Not on the A320 series. If you are at full power on those and you do not want to move E.g. maint grnd run, you have to use the toe brakes to apply full braking pressue to prevent you from moving

Isn't that what I said?  Wink

Quoting Starlionblue (Reply 2):
The brakes (note spelling) can hold the aircraft even if the engines are almost at full thrust.

Yes I know the original poster was talking parking brakes, but I just said brakes.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDoug_Or From United States of America, joined Mar 2000, 3421 posts, RR: 3
Reply 20, posted (7 years 6 months 4 days 11 hours ago) and read 32767 times:

Quoting Goldenshield (Reply 12):
There are always exceptions to the rule. I remember reading something about that in regards to loss of airflow to the rudder on aircraft of that configuration; however, is that a -200, or -7/900 we're talking about? At tight airports (BUR, SNA,) I would figure that policy could lead to possible 'issues.'

It is -200 through -900, but the policy is to stop the airplane on the runway, not applying brakes untill below 80 knots unless neccesary. At most airports this works fine, but obviously there are runways were brakeing shortly after touchdown is neccesary.



When in doubt, one B pump off
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 21, posted (7 years 6 months 4 days 10 hours ago) and read 32767 times:

Quoting InnocuousFox (Reply 17):
Jake Braking is the technique mentioned before of downshifting to use the high engine revs to slow down a truck.

I dont' think it's a technique so much as it's a specific mechanism fitted to many road-going diesel-powered trucks/busses. "Jake" is just a brand (Jacob) of compression brake, which releases compressed air from combustion chamber after the compression stroke so that it doesn't return any energy to the un-fueled power stroke. This is the noisy part, and doesn't necessarily involve high revs. Regular engine braking in a diesel (not very effective) or gas engine is simply a technique, and isnt' noisy.

O



Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineCaptainJon From , joined Dec 1969, posts, RR:
Reply 22, posted (7 years 6 months 4 days 10 hours ago) and read 32767 times:

Quoting Starlionblue (Reply 19):
Yes I know the original poster was talking parking brakes, but I just said brakes.

Yes I was referring to parking brakes, not break wind. I know the difference, I was rather sleepy when I typed it up so when I proofread it, I read it wrong.



User currently offlineTristarSteve From Sweden, joined Nov 2005, 4022 posts, RR: 33
Reply 23, posted (7 years 6 months 4 days 2 hours ago) and read 32767 times:

Quoting Starlionblue (Reply 10):
On pretty much any modern car, the electronics will cut fuel flow to idle when using engine braking.

I was under the impression that, in a fuel injected car, when you take your foot off the accelerator to slow down, the injection system cuts the fuel to zero and you are running on air.
This is why it is fuel efficient to leave the car in gear while going down hill. You use less fuel than if you put it into neutral as then you are idling, and using fuel.
Is this correct?


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 24, posted (7 years 6 months 3 days 22 hours ago) and read 32767 times:

Quoting TristarSteve (Reply 23):
I was under the impression that, in a fuel injected car, when you take your foot off the accelerator to slow down, the injection system cuts the fuel to zero and you are running on air.
This is why it is fuel efficient to leave the car in gear while going down hill. You use less fuel than if you put it into neutral as then you are idling, and using fuel.
Is this correct?

Wichever the case (idle or zero) GQFluffy's car seems to be malfunctioning. Then again, it is an American car so I wouldn't expect any less.  Wink



"There are no stupid questions, but there are a lot of inquisitive idiots."
25 Brettbrett21 : Do jets taxi on idle, aside from power-up to get going? What about props?
26 InnocuousFox : I would suspect that it is very similar to a car. As you mentioned, there is an initial powerup to get going. After that, the only relevant Newtonian
27 SilverComet : Turboprops also taxi on idle. They need an initial power up to get them going just like jets do, but once they get going their momentum keeps them mov
28 Brettbrett21 : I've watched Ryanair 737-800's at Luton come off of the runway and then taxi in at what looks like around 30-40 knots and then apply reverse idle to s
29 Starlionblue : Correct. A lot of pilots also complain about idle being a bit too much thrust for taxi. I was talking with a pair of CRJ pilots who complained about
30 Someone83 : And why do several airline have in their Op. manual to only taxi using one engine with turboprops to save fuel? If they only where running at idle wo
31 Starlionblue : Yes. Consumption is still lowered significantly by turning the engine off.
32 Post contains images SilverComet : Every little bit helps. At some airports taxi time can take up as much as one hour, with congestion and all. Even at idle the engines are still burni
33 HAWK21M : Which are these Airports. regds MEL
34 SilverComet : LHR, for one. It has happened before that one tonne of fuel be burnt on ground during the taxi leading up to departure, due to congestion at LHR. Oth
35 Starlionblue : Has happened to me numerous times at JFK.
36 Post contains links and images InnocuousFox : STL was horrible back in the TWA days. View Large View MediumPhoto © Bevin Shively
37 TWAL1011727 : I would much rather use brakes on my car than downshifting (maunal or automatic) under normal conditions. The brakes are alot cheaper to replace than
38 Bond007 : Similarly, thrust reverser maintenance costs more than the savings to the brakes. Jimbo
39 Goldenshield : No disrespect, but if one downshifts a stick properly, he will only go through a few brake pads before he has the clutch plate replaced, and not near
40 Starlionblue : On older cars, you also run the risk of brake fade if you brake a lot. I'd rather combine brakes and engine braking. It's not as if the clutch on a m
41 HAWK21M : Considering the Taxi time utilised & the unnecessary fuel burn.That would be a big hit to Airline profits.Why wasn't spacing provided. Is it still co
42 Scooter01 : That's why you should have the brakefluid changed once a year. -No matter the age of the car- Scooter
Top Of Page
Forum Index

Reply To This Topic How Do Planes Taxi Exactly?
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
How Do Planes Fly? posted Mon Aug 5 2002 11:00:40 by BigPhilNYC
How Do Planes Navigate Over Water? posted Mon Sep 10 2001 01:25:07 by Crank
How Do They Keep It Centered On The Taxi Line? posted Sun Apr 13 2003 06:52:52 by Shawn Patrick
How Do Pilots Stay On The Taxi Line? posted Mon Mar 18 2002 12:37:29 by AMSMAN
How Do Rockets Maintain Stability At Liftoff? posted Sat Apr 7 2007 02:00:44 by Comorin
How Do Jet Engines Work?: For School Project posted Fri Mar 9 2007 21:31:10 by YYZflyer
Students - How Do They Try To Kill You? posted Tue Feb 20 2007 18:03:57 by CptSpeaking
Intersections- How Do They Work? posted Sun Dec 24 2006 03:06:01 by HighFlyer9790
How Do You Make Time Fly By On The Flt Deck? posted Mon Dec 18 2006 23:02:51 by INNflight
How Do You Track Flight Hours posted Fri Nov 3 2006 19:09:33 by Airfoilsguy
How Do Planes Navigate Over Water? posted Mon Sep 10 2001 01:25:07 by Crank
Hydraulic Lifts For Planes, How Do They Work? posted Wed Dec 17 2008 09:30:46 by SXDFC
How Do Pilots Find The Taxi Ways? posted Fri Nov 28 2008 18:31:36 by B747forever
How Do Airlines Paint Rented Planes? posted Wed Jan 9 2008 17:19:50 by NWA320
Planes That Drag Huge Banners, How Do They T/o? posted Sun Jul 29 2007 14:10:36 by Lehpron
How Do They Keep It Centered On The Taxi Line? posted Sun Apr 13 2003 06:52:52 by Shawn Patrick
How Do Pilots Stay On The Taxi Line? posted Mon Mar 18 2002 12:37:29 by AMSMAN
How Do You Taxi To The Runway? (pic) posted Wed Aug 15 2007 23:46:06 by Aeroflot777
How Do Planes Fly? posted Mon Aug 5 2002 11:00:40 by BigPhilNYC
How Do Planes Navigate Over Water? posted Mon Sep 10 2001 01:25:07 by Crank
Hydraulic Lifts For Planes, How Do They Work? posted Wed Dec 17 2008 09:30:46 by SXDFC
How Do Pilots Find The Taxi Ways? posted Fri Nov 28 2008 18:31:36 by B747forever
How Do Airlines Paint Rented Planes? posted Wed Jan 9 2008 17:19:50 by NWA320
Planes That Drag Huge Banners, How Do They T/o? posted Sun Jul 29 2007 14:10:36 by Lehpron
How Do They Keep It Centered On The Taxi Line? posted Sun Apr 13 2003 06:52:52 by Shawn Patrick
How Do Pilots Stay On The Taxi Line? posted Mon Mar 18 2002 12:37:29 by AMSMAN
How Do Pilots Taxi So Perfectly? posted Mon Dec 3 2007 11:24:41 by DL767captain
How Do You Taxi To The Runway? (pic) posted Wed Aug 15 2007 23:46:06 by Aeroflot777
How Do Planes Fly? posted Mon Aug 5 2002 11:00:40 by BigPhilNYC
How Do Planes Navigate Over Water? posted Mon Sep 10 2001 01:25:07 by Crank
Hydraulic Lifts For Planes, How Do They Work? posted Wed Dec 17 2008 09:30:46 by SXDFC
How Do Pilots Find The Taxi Ways? posted Fri Nov 28 2008 18:31:36 by B747forever
How Do Airlines Paint Rented Planes? posted Wed Jan 9 2008 17:19:50 by NWA320
Planes That Drag Huge Banners, How Do They T/o? posted Sun Jul 29 2007 14:10:36 by Lehpron
How Do They Keep It Centered On The Taxi Line? posted Sun Apr 13 2003 06:52:52 by Shawn Patrick
How Do Pilots Stay On The Taxi Line? posted Mon Mar 18 2002 12:37:29 by AMSMAN
How Do Planes Navigate Over Water? posted Mon Sep 10 2001 01:25:07 by Crank
How Do Airlines Clean Planes? posted Tue Feb 19 2013 17:55:23 by cosyr
How Often Do Planes Get Repainted? posted Tue Oct 2 2012 19:13:11 by SXDFC
Hydraulic Lifts For Planes, How Do They Work? posted Wed Dec 17 2008 09:30:46 by SXDFC

Sponsor Message:
Printer friendly format