Ryanair B738 at Mallorca on May 29th 2014, wheel well fire indication
 

From Aviation Herald:-

Am I right in thinking a Boeing 738 can be landed at any weight in an emergency? Palma has 3200m R/W too so wouldn't have thought it a problem.

Not sure if I would have held in the same circumstances but it wasn't my call in this case -safe outcome was the main thing.

You assume the Fire indication remained after the Gear was extended.

Maybe, just maybe the Fire warning extinguished after Gear extension so they decided to land a bit lighter.....maybe at MLW.

I can't imagine anyone flying around burning off fuel with a Fire Warning....

The comment about finding "no trace of fire, heat or smoke" after landing by the fire service makes me suspect a possible spurious warning, but maybe not? It's happened before on the 738, which led to a runway evacuation; which in the end resulted in the company suggesting it was unnecessary. Hard one to get your head around as most evacuation procedures trained and checked in the sim are a result of a fire warning that can't be extinguished. This goes for the vast majority of carriers. I noted the Cathay 330 guys stating the same after their successful landing and evacuation following their fuel contamination incident.

The fact that they held to lower the landing weight and didn't evacuate suggests the light went out after the QRH was actioned. Otherwise, you're landing. Good work I'd say. We'll done to the crew.

Good point - in which case I would probably have done the same. As you say , holding very unlikely if the warning was still present !

Guess I was in "sim" mode!

From an old Boeing Flight ops review....worth a read.


There is a common misconception amongst crews that wheel well
fire warnings are caused solely by overheated brakes. Overheated
brakes can contribute to wheel well fires if they become hot
enough to ignite the tires, hydraulic fluid or other flammable
substances. However, our engineering analysis of the fire
detection system indicates that the brakes alone can not generate
enough heat to trigger the fire detector system.
Experience has shown that in most cases, extending the gear to
cool the brakes as well as the wheel well area produced good
results in coping with wheel well fires. However, there have
been incidents where extending the gear did not resolve the
problem. One such example was an incident where the electrical
lead to a hydraulic pump in the wheel well shorted and burned a
small hole through the hydraulic pressure line and ignited the
spraying hydraulic fluid. After the gear was extended, the fire
warning light extinguished but the fluid from the ruptured line
continued to burn. In this incident flames actually reached the
cabin floor area.
Incidents like this are very rare but cannot be disregarded.
Accordingly, the procedures in all Boeing Operations Manuals were
changed to give flight crews better guidance for coping with
wheel well fires and to emphasize that the wheel well fire
indication should be treated with the same serious consideration
as other fire indications. This change includes a requirement to
land at the nearest suitable airport.
In addition, crews should consider leaving the landing gear
extended unless retraction is necessary to reach the nearest
suitable airport. Every effort should be made to insure that a
wheel well FIRE is extinguished before the landing gear is
retracted.
In summary, remember that the cessation of the wheel well fire
warning does not guarantee that the fire is extinguished. It is
difficult or impossible to know the extent of the damage to the
wheel well or landing gear. Crews should treat a wheel well
fire warning with the same respect as any other fire warning:
Land at the nearest suitable airport and if conditions permit,
leave the landing gear extended while enroute to that airport.

Without wishing to be a "Monday Morning Quarterback" I can't help thinking that a fire warning (even if subsequently extinguished ) is a pretty good reason for an immediate landing , even if overweight, which Boeing say is no big deal if the landing is smooth. . . . . Ah yes, I guess that may have been the problem. :D ;)

In an emergency you may land the 73 at any weight, but if it's above Max Landing Weight it requires an over weight landing inspection.

The QRH does not make any reference to wether the light is still on or not.
It plainly says/suggests to plan to land at nearest suitable airport - which they then did.

Why it took 30min - if true - to plan this might be a different story, hopefully not one about "Landing Weight" or of missreading the "20minutes" .... :E

In summary, remember that the cessation of the wheel well fire
warning does not guarantee that the fire is extinguished.

It plainly says/suggests to plan to land at nearest suitable airport - which they then did.


The above are quotes from 2 previous responses. In the former, taken from a Boeing memo, this does not appear in any Boeing pilot issued document that I have see, While it might be good airmanship this advice is somewhat hidden. Equally I've not been aware of the concept that a wheel well fire warning was associated primarily with hot brakes. I've had such a false warning in a phase of flight where it was nigh impossible to have come from hot brakes. We mdd an immediate return to field of departure; taking about 15 mins from a medium FL. The QRH procedure did extinguish the light. I discussed with the F/O the possibility of a combined hydraulic leak (fine spray) and an electrical spark. No way of knowing. What I didn't appreciate was that an extinguished light might not be honest.

In the 2nd one the 'land at nearest suitable…' in various companies and sim scenarios has never been emphasised as ASAP. When I did have various fire warnings, then extinguished, in sim scenarios, and elected to land ASAP, I was chastised for not going through the 20 minute stage play of QRH, CRM, NITS, Ops call, PA, set up FMC, brief, etc. etc; even though we had just taken off from a base airfield with OK weather. A spin round the circuit was heresy.
I think Boeing should do better to clarify and inform crews just what these sensors are telling them, or not, and to outline just what is expected of the crew. The response from T.C's in various airlines was interesting if confusing. What was good airmanship in one was forbidden in another.
Having said that, in one LOFT with the latter type airline, with an inextinguishable engine fire after takeoff it was deemed sensible to rip it around and down ASAP: much to the amazement of the SFO who wondered what the hell I was doing.

From what the Boeing memo says, i.e. a WW fire warning extinguished does not mean the fire is out = should mean on the ground ASAP and NOT holding to burn off fuel. Crews do not seem to appreciate this.

If I get a wheel well fire warning light, I do not even try to recall maximum landing weight. If the light goes out after extending the gear, it might put me two inches backward on my seat, however it will not change my decision to put that 737 on the next runway.

We discuss the sensors then with a coffee.

We discuss the sensors then with a coffee. = Common sense

stage play of QRH, CRM, NITS, Ops call, PA, set up FMC, brief, etc. etc
= Stageplay is spot on. Some use it that way.

I've been flying B737 now for 20+ years without a wheel well fire indication. But I don't think I would make the most out of it should it RING one day. The stage play is overstressed sometimes, methinks.

Yes, I think so, too.

On the other hand, I think we can assume that they were taking into account all the external info they had available, such as cabin reports, ts and ps etc, and even then, with a quick performance review (accepting the overweight landing, as 1100kgs or so of fuel won't make that much difference) and setting up the arrival, and PIOSEE, DODAR or whatever, it's surprising how quick that 30 minutes goes.

And also, they know very well that the decisions made in that 30 minutes will be deconstructed at leisure over the next several weeks by the company. It's all very understandable.

You're on fire and you want to start running performance numbers? If the runway is over 6500', I'm using it! Falp 40, full reverse and max brakes, you'll fit (unless contamination or ac system failures are an issue). A fire is no time for PIOSEE/GRADE or whatever other PC conference/handholding the company likes. A fire should result in a landing in minutes, just the time taken to manouver the aircraft.

Exactly. And contemplating what the analysis by management later will be, is my last concern.

That all reads like a sim de-brief!

So in that vein.

Why did the wheel well fire warning come on?

A fire should result in a landing in minutes, just the time taken to manouver the aircraft.

True, but once again I throw on the table that if the warning has gone out, and there are no other signs to suggest that the fire is still burning, then taking as little time to ensure a successful outcome is what most would do. That does not necessarily include burning fuel to reduce landing weight by a coupe of tonnes. (The a/c isn't going anywhere without an engineering inspection, which could therefore include an overweight landing check.)
The area of confusion, and mitigation, is where Boeing says that an extinguished WW fire warning with there gear down does not guarantee the fire is out. That to me is the shocker. I've run this scenario in the sim under guidelines from the company, and of course the fire warning goes out and they want the whole 9 yards of return landing preparation. On the ground, the fire stays on, and they want the pax-evac exercise performed. These are tick in the box sim scenarios. I'd prefer the WW fire in the air where it doesn't go out. Now what?
Boeing need to disseminate better information to pilots about the validity of extinguished warnings, AND to better define what "land at nearest suitable.." really means. You've a small unfamiliar minor airfield at 20mins from CRZ and a familiar major engineering base at 40mins from CRZ. Which are you going to drop into?

Why did the wheel well fire warning come on?

When I had it at medium level it was traced to faulty wiring and a sensor. I then discovered it was the 5th time in the fleet during that year, on different a/c, and I'd never heard of it. How many worldwide?

Why did the light come on? Why did it extinguish?
 

It is worth remembering that the loop detecting the WHEEL WELL FIRE is a single loop installed int the wheel well itself, triggering an activating of the light at a predetermined temperature, extinguishing the light at a predetermined temperature.

Thus, it may well be that the gear extension has caused the 'hot' parts (if located not the landing gear assembly) to be now located in an airflow sufficient to extinguish the potential fire and/or cool down the hot parts causing the activation of the light.

Furthermore the removal of these hot parts from the vicinity of the loop will cause the loop to reach the predetermined minimum temperature soon and the resultant will be that the light will be extinguish.

Thus the statement from the Boeing Memo as supplied here bears truth.

Should however there be a fire located not on the extended landing gear assembly, the loop continues to sense the fire temperature range and remains on. This would be an indication to the crew that the fire is indeed in the wheel well and not part of the landing gear assembly. Reasons for this could be plentiful, the described hydraulic incident in previous posts being one such reason.

It cannot be emphasised that the loop is a temperature detection loop only and its location is not on the landing gear but inside the wheel well itself.

Given the fact that the crew came from an airport where IDLE landings are often achieved by said operator and brakes are not often subsequently released to cool the heat stack ons stand, with no evidence of fire or excessive heat after the landing, it may be wise to look at the aircraft's history prior to the incident and to not just look at OFDM data from the flight but of the flight arriving prior in PMI. Furthermore as OFDM does not capture ground events after shutting down engines, this may be our only clue to possible hot brakes which may have required cooling to take place.

PS: In PMI 24L is not commonly used for departures, which sounds a bit odd in the initial post of the incident. For landing 24L it provides a rapid exit S1 which can be especially useful for aircraft parking North of the terminal to vacate, but this requires a very short landing distance to be achieved and consequently a high use of brake forces to achieve it, especially with common tailwinds on that approach resting in higher ground speeds on touchdown. Reversers have little effect when LDA is so short due to the deceleration rate of the aircraft and spool-up time of the engines to reach reverse thrust level of >70%.

Forgive the ignorance of a non pilot but if my local bus can have multiple cctv cameras all over it so the driver can see what is going on in his vehicle, shouldn't aircraft have a similar arrangement so the crew can see what is happening outside the cockpit?

Just to clarify, the "notice" is a Boeing FLT OPS review, no 737/18. Whilst it is old (1991) I have just checked and it is still shown as active on the My Boeing Flight Ops area, so I assume is still seen as relevant and accurate.

Rat, I agree with all of that.
My question "why did the wheel well fire warning come on?" was somewhat rhetorical, and directed at the Bang it on ASAP thinking.
One scenairio:
You fly a wingover and roll out onto 5 mile finals, rattling through what you can of the checklist. Maybe you don't notice one, then the other B sytem light coming on. The flap/gear config warning is just a distraction, now. And as you scoot down the runway you realise that the Flap40, normal brakes, max reverse you were relying on is not there. Or one of the tyres.
Afterwards at the investigation, the surviving crew member says she heard lots of banging just after take-off, which got worse when the gear went up, and stopped when it went down again, but the flight deck never did get onto the interphone to discuss it.
Maybe you were sharp enough to go around, sharp enough not to retract the gear. But you've saved no time.
Some kind of failure management, however brief, is time well spent.
Boeing, themselves say "Plan, to land at the nearest suitable airport. (my bold).
As for cameras. Yes, it would be nice. It shouldn't be too expensive these days, particuarly with clean sheet designs. But unless you make it a no-go then departing with u/s cameras puts you in the same situation.
All the above just my humble, although I have at least been in "Land at nearest..." a few times.