Flat tyre?
 

How do you reckognize a flat tire on large transport aeroplane, e.g. taxiing for takeoff ?

(No tyre press ind sys installed)

One of the tyre manufacturers has a poster with photographs showing just how difficult it is to see a deflated tyre.

If you have a serious doubt get the pressure checked.

Failing that kick the tyre. Doesn't do any good at all but it's never stopped anybody doing it!!!!!!!!!

:D Indeed! Everybody loves to do that, be it a car or a bike; Never knew they do this on planes. I would imagine a very long walkaround on a 747. Who pays for the shoes anyway?

Nothing more to what the gentelmen already described,if you are doing the taxiing, you'll feel the need to put pressure on the tiller.......plus all of what is mentioned above

Look at this...

http://www.flightsafety.org/ap/ap_sep93.pdf

Is your aeroplane equipped with

- wheel well fire warning/protection
- tyre pressure indication
- brake temp indication

???

Considering that for about £4 each you can buy an indicator valve cap for auto tyres, that pops out a red indicator if the pressure drops below around 30 psi, I'm surprised no one has made them for the aviation market. Not to be used as a reliable indicator that the pressure is OK, but as an indicator that the pressure is probably low.
Bet everyone would still kick the tyres though.

I had a tyre deflate on me on the taxy-out, after startup in the 747.
There was a little vibration on takeoff, but nothing much more that the previous takeoff. First we really knew about it was that the tower (Shanghai) asked us as we passed through 3,000' if everthing was okay because "on takeoff your landing gear was letting out sparks and maybe fire."
Anyway, we landed the plane just fine but the other tyre let go and the debris did quite a lot of damage to the fuselage. Still didn't feel anything odd on the landing either, and probably would have taxied all the way to the bay if we didn't know - I pulled it up just off the runway, to clear it as I knew the plane would be stranded for a while.

At least it only gets flat at the bottom.

Paul Wilson: on the 757/767 and most other large a/c each tire has its own pressure guauge built into the tyre/wheel assembly that gives the current pressure and Mr. Boeing kindly writes the required pressure some where on the gear struts.

Some aircraft have a onboard pressure indcation system but is usually only offered as a rather expensive customer specific add on - perhaps for larger types destined for short turnarounds I.e. the 747-400D.

As for flat tyres or the more exciting burst tyre on take off: Various advice is given from training manuals but they all state the same thing, don't reject the take off for one and on the 757/767 a single tyre lossed on a main bogey is a deemed a relative non-event when it comes to landing. Runway length permitting.

I was told many years ago that on a twin-wheel unit, when one deflates, the squashed-at-the-bottom tyre is the good one - the deflated tyre looks perfectly normal but without the load-carrying deformation.

Doesn't help in the air though, does it.

Would you stop for a bang/vibration (that might be a tyre burst) at any speed up to V1?

If you have a flat tire don't you have to change the opposite tire on the same axle, because the good tire could have been over stressed?

@glhcarl
 

Yeah, that's what I know about.

What I wanted to point out is the risk of a wheel well fire due to unknown tyre failure (flat tyre), e.g. if you don't have a Wheel Weel Fire warning system and no tyre press ind. sys. you may be in trouble if you take of with a flaty.

The view of the sidewall will have a bulge.
regds
MEL

This is one of the reasons that, at least on the NG , you won't be able to retract the landing gear if the tyre is damaged.

@alexban
 

How does this work?

There are some sensors ,or fittings, on the wheel bay edge ,and when a spinning tire with loose tread impacts a fitting in the well ring opening ,the gear stops retracting and free falls back to the down position.The affected gear cannot be retracted until the fitting is replaced. Smart,right?

@alexban
 

Thx, never heard about this one.

Frangible Fitting 737NG
 

The frangible fittings are in the retract hyd line for the MLG, when a flailing tread from a damaged tyre strikes the end of the fitting, it actually breaks off & ports the retract pressure to athmosphere, stopping the gears retracting.
It has to be a dual failure for it to function, a damaged tyre and a failure of retract braking.
The fittings protrude below the wheel well slightly, where they will be snapped off by flailing tyre tread, providing the retract braking has failed to stop the wheel rotating. all a bit agricultural.

Exactly the Frangible fittings are located in the MLG Wheelwell on the B737NGs.
The NLGs don't have them.
regds
MEL

kicking tyres---
 

one should be able to feel the difference.

perhaps a bit subtle but should give a clue.

the only two flats i had, i didn't do the walk-around! both on 737's which have dual wheels.

and it was the push back crew that noticed the difference during push-back.

at least in San Diego, he said he had been trained to look for that and knew what a flat tire (US spelling) looked like.

the other was in heathrow and he wasn't as talkative about his experience. simply said it looked flat.

both indeed were flat.

@stator vane
 

Same happened to us. So my concerns are

- no tyre pressure indication in cockpit
- no wheel-well fire warning/fighting
- no daily manuell pressure check.......

and you start taxiing 4 miles with a heavy-weight aircraft for takeoff:\

Tyre pressure is checked daily by your ground engineer. As for wheel-well fire detection, Airbus is relying on brake temp indication for that.

@Clarence Oveur
 

Yes, I know. Did you ever check the MEL about break temp ind sys.......?

To make it clear for everybody. Airbuses don't have a wheel-well fire warning, some even don't have a tyre-pressure-indication in the cockpit either.

The only thing left to detect a possible fire in the wheel-well is the brake-temp-indication, which may be inop if brake cooling-schedule is observed....

Yes, I do know what the MEL says about brake temp ind. I also know a bit about the analysis required before items can be included in the MMEL.

No doubt the first chapter of your company MEL will state that the commander can refuse an aircraft with inop equipment, even if the MEL says it's a GO item.

If you feel so strongly that it is unsafe not to have tyre pressure indication in cockpit / wheel-well fire warning / brake temp ind. there is only one thing to do.

If you feel so strongly that it is unsafe not to have tyre pressure indication in cockpit / wheel-well fire warning / brake temp ind. there is only one thing to do.

Yes, I fully agree.

Tyre pressure indicators
 

Paul Wilson,
You quote about four quid for low pressure indicators for car tyres. By the time it has been approved, certified and anything else that can be thought of to bump the price, I think you would have to be thinking of at least ten times the cost for a car. (Even though it is identical).

World of Tweed,
I think you are referring to the inflation valves incorporating a pressure gauge, If so these are optional to the standard valve stem installed on wheels. I have worked on several operators B757s and never had them fitted to this aircraft. I have, however, seen them on other types, and not necessarily on every wheel. They are useful, as it saves carrying a tyre pressure gauge on a walk round and, are calibrated to within 10% accuracy,when new.

Check the brake temps during the taxi. If one is significantly lower than the rest the tyre may be flat.

smudge

Not so sure about low pressure doing that.........depends how low, 'low' is I guess.

No pressure on the other hand. Unless you spot the deflated one on the walk round, and believe me you could easily miss it- even if you kick it, NO pressure will cause no torque to be passed into the brake pack. The brake normally converts the torque into heat, so no torque- no heat.

If you land and one brake temp stays very low- you've got a flat.