Valve cap missing
 

Looked around for information on this subject but no luck, is a valve stem cap required to be installed prior to flight, I made our reluctant engineers produce one prior to our flight today. A321 MLG.

The sign off "none in stock, ADD raised". :confused:

The valve cap is the primary seal.

The is nothing in the MEL/DDG to allow you to defer .

:=

no it's the secondary seal, there's many things not in the MEL but you can still go!:eek:

Clearly not a safety of flight issue, probably should have went on record in your NEF program "may be what an ADD is". He did his job correctly, sounds like you are being a p:mad:ick and have intent to burn the guy.

Well I'm not really looking for someone to take my side, I am simply the last line in the Safety chain and want to ask the experts about the subject, and as Golden Rivet points out, it is not listed in the MEL.

Grounded27, it sounds like you have some major issues with flight crews, whatever your problem is, from your point of view, if the engineer followed proper procedure, how would I possibly burn him by delaying the flight until they find a valve cap, I would be the one having tea and biscuits with the CP?

Cheers, D.L.

spanners,

Erm, if it's not the primary seal, what is it's purpose and how come I was taught this many years ago and indeed, it is still taught today ?...we could get into the realm of semantics here of course,...dust cover vs primary seal..and then there's the cover for acc.charging points of course...;)

dream land....to be honest, you seem to have turned a non event into an event. A missing primary seal is hardly a stopper now is it?....and your comment about " I made " the engineers etc, etc, suggests you have taken the "I am the captain, do as I say " line....rather than, er, talk with the engineers and come to an agreement. Nobody is going to jeopardise an aircraft now are they...?

Why didn't they just take one off another wheel assy, ... and even if it was a line station, they would have a couple of spares...and then order a new one...simple solution really.

the cap i think you are referring to is for the charging valve of the mlg?
having a lot of experience working on landing gear i would have considered this as a cover to prevent dirt entering in the valve. the charging valve itself has a special operation. it needs to be loosened twice before you can service the gear.
regarding dispatch for sure you can fly without this cap so raising a HIL was the right thing to do.
you can also see them on brake bleeding ports, door accumulators as well as the resevoir charging port. there are a lot more.
hope this helps

If you want to have everything listed in the MEL, there wouldn't be an aircraft flying anymore. The MEL would also get really big:E

The wings aren't in the MEL, but you'll be needing them for an on time departure. Granted, the MEL preamble provides you with a statement along the lines of 'non-airworthiness items are not included'. But as far as know, the only person that can make this determination is the manufacturer.

many things attached to the wings are in the MEL so not a valid argument

So if that's your opinion you would ground an aircraft because of a piece of missing carpet (not in the MEL) while waiting for permission of the manufacturer

Given the number of tire changes that are carried out on the ramp by line mtce personnel, I'd venture to say that a majority of engineers have spare caps either on hand or close by.

I'm surprised that the LAME in Dream Land's situation couldn't produce one.

K 'n c, the valve core is the primary seal. Is the cap considered a secondary seal or simply a dust cover? Let the thread continue :)

rgds

cod

We once had a 3rd party customer 747 arrive with about 4 of the 18 caps remaining, suffice to say we didn't have enough for the rest of the wheels so DD'd them. I seem to remember there was something in the classic MM about the caps being a secondary seal so was quite happy to DD them. Unfortunately don't have those manuals anymore so can't look.

Anyway I could of course be wrong, it has been known :eek:, perhaps I have learnt something new again today.:ok:

http://www.airmichelin.com/uploadedF...ice_manual.pdf
This pdf from a manufacturer implies (p49 I think) that the cap is solely to keep dirt out. Surprised the hell out of me because I have always believed that the cap was the primary seal.

So there is no need for a core then..:ugh::ugh:
A Valve cap is exactly .. a cap to protect the valve! :E

well before the thread is led astray. I just want to specify that i am talking about the A320 gear.from your comments it seems it is possible on other aircraft types that the cap has another function

The cap is a secondary seal. The primary seal is part of the valve core. The cap's functions are:

1: Prevent debris from entring the valve stem and depressing the core
2: To act as a secondary pressure seal in the case of core failure.

On an A320, a single tyre, let down under reletively controled conditions (core failure, so no explosive decompression), would not cause the aircraft to be uncontrolable on the ground. So worst case scenario is that you have one flat tyre. Its not in the MEL, so engineers must use COMMON SENSE / ENGINEERING KNOWLEDGE to dictate whether the aircraft should fly or not. Thats why you get paid big bucks! :ugh:

ASFKAP... You mean there is a danger of brakes being fodded??:E

I was taught many years ago that the cap is the primary seal. The valve is there as a convenient device to allow one to inflate the tyre and act as a secondary seal.

Was I led up the garden path all those years ago? Possibly, I'll have to dig out my copy of CAIPS, maybe it's in there.

It used to be a CAA oral question, How can you tell if the cap is servicable?

Answers on a post card........:ok:

I brought up an acronym before NEF, it is used widely under FAA governance and would surprise me that every other CAA does not have guidelines for aircraft operaters to create a seperate lits of Non Essential for Flight items to be repaired or replaced usually before the next c check. NEF items are often AMM items. When not covered by the AMM or MEL a NEF item is generally approved for a non mel deferral by the operators maintenance controller. Are there not programs like this in the EU?

Education on this matter may help the OP from asking questions like this in the future.

Thanks to all the posters, to be clear, it involved one of the main landing gear tyres, I told them I wanted it installed, it was from our maintenance base and the base for 25 similar aircraft. After another 10 minutes one was found and installed. I did t have a clue whether there was a safety issue involved. Iwas sure the engineer was wrong, but apparently I was wrong. :eek:

Cheers D.L.

At least we all now know why so many aircraft have valve caps missing.

They are all in ASFKAP's pockets and gash box;)

Dream Land
 

Just bought you a virtual beer, sorry if I misread into the intentions of your OT.

Cheers,

Grounded

Grounded27, cheers mate, thank you. :D:D

Fascinating little thread about..... " the primary and secondary functions of the dust cap sealing device "...:D ;)....

The really worrying bit is the lack of acumen shown by said line engineers however ! :ooh:

Dream Land was right to insist, the valve cap is there to prevent leaks and dirt ingress.

From the AMM wheel inspection A320

I read from his original post that this was deferred as an ADD and Dream Land asked the engineers at his main base to sort it when he got there. Exactly the right thing to do in my opinion.

The Hitcher
 

The difference between your bike or car whatever, is that the cap on an aircraft wheel is made of metal, with a seal and can be tightened with a spanner (wrench to our American cousins).

Ok Hitcher, which are you?

Next time I see someone with a valve cap buried in his face i'll know who's advice he has taken.

If the valve core fails what do you think will stop the air leaking out?

Hitcher,

Your first post was fair enough...NO problem with that and as you admit, you've never been near a crewroom, ramp, line, hangar or flight deck etc in your life otherwise you would be aware of the capacity of engineers and F/D to " discuss at length" as they say to prove a point...sometimes these, ahem . discussions can get rather "warm" and even, possibly " a little animated " .

This one hasn't...:ok:

Your second however, suggests you need to carry out a functional check on the location of your larynx....... :E

Schrader valve - Wikipedia, the free encyclopedia
so this type of valve is a schrader valve. although wikipedia it does give the function of the cap. it is NOT a secondary or primary seal of any sort. it is only to prevent dirt entering the valve

And how many `gingerbeers` would check the tyre pressure before replacing a missing valve cap ??

sycamore,

Fair point...or just fishing....or just being holier than than thou ?

Rhetorical question.....how many drivers would notice one was missing...on a wet / cold night at 00 silly hrs doing a walk round?.

Oh Dearie dear. Feathers are about to fly.:ooh:

The Hitcher said -

Anyway, back to valve caps. Anyone found any legal doc for the Airbus that says you can defer a missing cap?

With the plastic bicycle or car type cap, agreed - they do not act as a secondary seal, but aircrat ones do! As said earlier, they are designed for the function of keeping air in the tyre in the event of primary seal failure. (Metal + torque setting... usually 6lb/in, ie. calibrated-finger tight).

As a ramp tramp (semi-retired) I would think twice about grounding an aircraft with a missing valve cap... just imagine trying to explain that one to the CEO.. but for the jockey to put in an ADD, no problem. It'll get done ASAP.

In Hitchers defence, flight safety is everyone's problem, so full credit for spotting the faults. As a security guard, his responsibility will cover the ramp and the aircraft on it, so I can see why he is close to the aircraft. He did not say he interfered with the aeroplane.

Can we just all get along please?

Guilty as charged milud.

Tech log certified as such too.

All this confusion between bicycle tyres, schraeder valves and the humble aircraft tyre. :ugh:

Bicycle tyre dust cap, plastic, cheap, keeps the dirt out and protects the thread. Same on my car.

Someone somewhere must have it in writing as it was drummed into us for years that the Valve Cap (on an aircraft wheel) is the Primary seal.

Now that would be a problem as all the wheels I know are filled with N2! :eek:

This is getting as good as the "How do you open a tin of oil" thread. :D

K-n-c,Turin, et al, I know it may have been a little tongue-in-cheek,about checking the tyre pressure as well; however what you do on your car is one thing,aircraft are widely different,and wheels and tyres suffer more than your average jalopy .The cap is there as a cover to prevent contamination of the sealing mechanism,from heat, dust, liquids,etc and to act as a second seal if the valve itself fails.If it isn`t there,it should be replaced,not by one you have lying in a tool box/pocket/ashtray,but by a new/clean one.Not only that but any `sensible` engineer should inspect the valve to see if it has failed,or is loose/damaged,and check the tyre pressure as a matter of course,as the tyre may have a failing valve.Consider also the fact that the valve cap has a certain mass/weight,not a lot, but on take-off and landing it can be accelerated to a speed of up to 300 ft/sec on large aircraft.It`s energy probaly won`t punch a hole in the airframe,but it may cut wiring or a hose,or jam in a brake caliper.And ,yes,I`ve done my walkrounds at oo.oo o`clock,from -30 to +40 wet or not,but prefer `normal` working hours now !!:ok:

Sycamore
 

Er...I think we agree... I think.


I'd still like to see it in writing though. :ok: