A320 idle reverse during taxi

[mike wess]

Can idle reverse be selected on A320 to control taxi speed on clean dry taxiways

[IFLY_INDIGO]

Well, you may select it at your own risk. Airbus doesn't talk about it at all, as far as my knowledge goes.

Unlike the turboprops, where it is a usual practice, I think it is not a wise idea to do it on A320, especially on taxiways where danger of FOD is higher than on the rwys..

I would do it on taxiways only in case of brake failure..


cheers

[VinRouge]

Why would reverse idle be more likely to cause FOD than Forward ide?

Not facecious, generally honest question.


Surely it wont make a difference? The TR jet generally is displaced UP isnt it?

If anything, tI would have thought it a more significant issue for prop aircraft, as all the muck is thrown forward, sucking up muck kicked up by the wheels?

[ITCZ]

Posted in a thread on 737NG idle reverse (http://www.pprune.org/forums/tech-log/261028-ng-reverse-during-taxi.html) on taxi:

From 320 FCOM (CFM's)

CAUTION

On taxiways, the use of reversers, even when restricted to idle thrust, may have the following effects :

-The engines may ingest fine sand and debris that may be detrimental to both the engines and the airframe systems.


-On snow covered areas, snow will recirculate into the air inlet, which may result in engine flame-out or roll back.


Except in an emergency, do not use reverse thrust to control aircraft speed while taxiing.

[mike wess]

Well the way it's written in my manual as follows:

- On snow covered areas, snow will recirculate into the air inlet, which may result in engine flame-out or roll back.Except in an emergency, do not use reverse thrust to control aircraft speed while taxiing.


In my opinion in this specific statement the part Except in an emergency... is only applicable on snow covered areas. Let me know what you think.

Thanks

[NVpilot]

Ridiculous to use any reverse during taxi on the A320, blade erosion, FOD, is that not enough a reason?

[Founder]

Could you please state a scenario in where you would want to use it? where normal brakes does not do the job?

[NZScion]

If you were taxiing way too fast? Your own silly fault for getting into that sort of situation to begin with...

[finncapt]

Stuttgart, taxiing for the westerly runway - can't remember what it is.

Hot day, heavy weight. To keep the brakes from o/heating - no fans when I flew the 320.
Did it often!!

[finncapt]

Didn't mention - it's quite a downhill slope!!

[RVF750]

It's a fact that brakes heat up if you taxi faster whether you apply braking force or not. The brakes are like a cars in that they don't have a space between packs, only light or heavy contact force.

If you are worried, keep your taxi speed down. Simple. Reverse is just going to cause wear and damage, if not today, then some day, especially on wing mounted engines close to the ground.

Brake wear can also be minimised by light dabs to keep the speed low, not larger applications from faster speeds.

It's always tempting to taxi faster, especially on long straight routes like secondary runways. where you have a good mile or more to get to the back of the queue.

Annoying as it is to see turboprops whizz past you, don't let it get to you. Slow and steady will keep the temps down. Or drive a 146 with big fans:)

[T-6]

With engine IAE the idle is very hight and sometimes I´ve seen aircraft taxing with idle reverse. I asked a friend who is flying IAE engines and he said that sometimes with aircraft without brakefans in a very long taxis they used in order to keep not too hot the brakes for departure ( 300 º ) but you will not find anything in the FCOM but this is the main reason.

[Dani]

VinRouge was asking why you shouldn't, and multiple answer was that you shouldn't..., well, so much for CRM.

The problem is that below a certain speed, air is faster blown forward from the reversers than the forward speed of the aircraft, so the air will get sucked in from the engine. This can cause engine stall, ice accumulation if ice/snow is sucked in and FOD particles are sucked in. This forward speed is defined by 60kts by AI and is more or less the same for every aircraft of this engine configuration. That's why you should always select reverse off under 60kts, unless in emergencies.

finncapt, it's very unwise if you use it in your situation in STR. It may help to take off with hot brakes, but following costs for engine overhaul will be much higher, or someone will maybe even have engine trouble. Better wait until your brakes are cooled down and then take off.

Dash&Thump, slow taxi is indeed the menu-du-jour, but not braking with light dabs. You have to brake hard. The suggested brake technique for cool brakes (and less wear) have been described here lately: Accellerate to max taxi speed (i.e. 30kts), brake it down to around 0 (5kts is more realistic), let it accellerate to 30kts again without braking and so on. When you brake, brake moderate, but brake remarkable. Never ride the brakes!

Dani

[ITCZ]

In my opinion in this specific statement the part Except in an emergency... is only applicable on snow covered areas. Let me know what you think.

I think your FCOM has a couple paragraph formatting characters missing. Happens all the time when a busy Flight Ops office transcribes material into its Ops Manual.

You gotta be careful you don't read things "too hard" until they say what you'd like them to say.

Example: I can find a passage in the Bible that says "There is no God."

Psalms 14:1, right there in black and white.

Read it hard enough (and ignore the preceding "A fool says in his heart...") and you have a great argument starter at your next overnight... or do you?

[Joe Monsoon]

Dani i agree :ok:

[Airbus_a321]

@finncapt
I agree. Nothing to add.

I use NOW the same technique (NOT procedure) after my (first and only) experience also at STR (nice coincidence).
It was a cold day, light a/c, engine a/i on, no brake fans, taxiing down for Rwy 25(?)
Probabely we all know well the delayed temperature rise on the brakes. Waiting on the RWY for t/o-clearance, then by our big surprise, we received the BRAKES HOT.:confused:
Result: cancelling take off clearance, exit the RWY on the next taxiway and queue again behind all the other aircrafts, waiting for the brakes cooling down.

From this time on I use IDLE reverse during taxi on a common sense base (as just a technique) .:8

[goeasy]

Exactly A321, and in fact, my FCOM says on landing you may use idle reverse down to taxi speed, which I do every landing. Gives much, much more control especially in wet/slippery conditions.

At busy airports, I cant see major taxiways having much FOD risk as they are 'blown clean' every few minutes.

[Torque2]

Does having Max Autobrake selected in preparation for the T/O affect the use of reverse idle? i.e. would the autobrake not function given the high taxy speed that is being suggested?: :confused:

[TyroPicard]

Only if you taxy above 72 kts.......

[the rim]

from someone who fixes them brakes are a lot easer to replace than engines .....yes brakes will heat up quickly but carbon brakes cool down as quick WHEN PARKED even without fans plus rev idle uses more fuel ....just use the brakes that what they are there for....same as your car

[NVpilot]

from someone who fixes them brakes are a lot easer to replace than engines .....yes brakes will heat up quickly but carbon brakes cool down as quick WHEN PARKED even without fans plus rev idle uses more fuel ....just use the brakes that what they are there for....same as your car. Thanks for the input.

[Airbus_a321]

@ rim :confused:
...but carbon brakes cool down as quick WHEN PARKED even without fans ...:confused::confused::confused:

What do you mean with ...as quick.... 20 minutes, 30 minutes. It depends how hot they are. You agree ??

...well maybe yours. My brakes don't cool down...as quick...

[NVpilot]

We land around 74 tonnes in conditions above 30 C, we use auto brake LOW and full reverse to 80 KTS, we have one hour turns and using brake fans is not required.

[stezam65]

Remember not to use idle reverse during taxi in after a strong braking during landing roll when you have strong tail wind because the fumes of jet blast and hot brakes can be ricirculated throughout air conditioning in the cabin. Bad experience encountered!

[10002level]

SOP is to deselect reverst thrust before leaving the runway in order to prevent FOD ingestion.