Thrust Whilst Taxying

[donnlass]

When an aircraft has landed and turned onto the taxyway heading to the ramp, they always have a boost of thrust, (normally when passing the Viewing Park at MAN).

What is this extra boost for? Is it because they have retracted the flaps back to up or just need more thrust to taxi in to the ramp?

Thanks lots:)

[Captivep]

I would say it's as simple as slowing down to make the turn and then speeding up when on the straight bit of taxiway. Or, if the aircraft is already on the straight there could be a slight incline.

Either way, it would have nothing to do with retracting the flaps.

[donnlass]

Thanks for that, could be just a bit of oomph needed after turning, they certainly do it when straight after leaving the active runway, must check if its the ones which turn early that do it more often.:ok:

[Dave Clarke Fife]

This may be one reason donnlass.....if you land on 23R then you are trundling downhill on a -0.4 slope from 249ft at the end to 212 ft at the 05L end. When you turn off 23R you are then moving up a +0.4 uphill slope and this combined with a bit of power to help with the turn could be the reason for the squirt of power.


Runway Information

Runway 05L/23R

Dimension:10000 x 150 ft / 3048.0 x 45.7 m Surface:Asphalt, asphaltic concrete, tar macadam, or bitumen bound macadam.

Runway 23R End Elevation:249.0 ft Slope:-0.4

Runway 05L End Elevation:212.0 ft Slope: 0.4

[donnlass]

This may be one reason donnlass.....if you land on 23R then you are trundling downhill on a -0.4 slope from 249ft at the end to 212 ft at the 05L end. When you turn off 23R you are then moving up a +0.4 uphill slope and this combined with a bit of power to help with the turn could be the reason for the squirt of power.


Runway Information

Runway 05L/23R

Dimension:10000 x 150 ft / 3048.0 x 45.7 m Surface:Asphalt, asphaltic concrete, tar macadam, or bitumen bound macadam.

Runway 23REnd Elevation:249.0 ft Slope:-0.4

Runway 05L End Elevation:212.0 ft Slope: 0.4


Thanx lots for your reply.

Please could you remind me is 23R coming in over Shadowmoss and 05L over Mobberly (Tunnel End)?

[Lord Spandex Masher]

Hi Donnlass,

I fly in to MAN regularly. You answered your own question.

Coming off the RETs on 23R there is a rather tight turn to head back up the taxiway. We have to take this turn at low speeds for obvious reasons*.

We don't like going slower than we have to so a handful of power is needed to get up to usual taxi speeds.


*Plus, as there are a few taxiway options and my F/O's are usually too slow contacting ground I have to wait until I know where I'm supposed to be going!;)

[donnlass]

Yes thats wise lol.

But seriously thanks lots.

Certainly sounds logical, probably would happen most with a/c turning short.

Do the ones that finish their landing roll all the way up to the end and then come past the Concorde hangar still need a squirt of power as well?

[Lord Spandex Masher]

More than likely, I'd have thought (don't usually end up that far down!), coming off 23R right at the end there's a fairly steep incline so quite a bit of thrust will probably be required.

For your interest we only really need to use more than idle power to get moving. Usually after we've overcome that inertia just idle power is enough unless we're manuevering. With carbon brakes lots of applications will cause excessive wear so we usually allow the speed to creep up to our max taxy speed (or whatever is sensible) then use one fairly firm application of brakes to slow down to a slowish speed before allowing it to creep up again.