Not every day an engineer, a normal, average engineer, like me, decides to write an article about a problem that he's experiencing; but it is about time that we all start doing it if we want to benefit from each other's knowledge in every possible area. In this case the problem, while a simple one, seems to affect a lot of other users. The Boeing fire handle lens cap is broken.

Introduction

That sounds like a problem you just see, and you think, well, it is not a big deal, I'll replace it; but when you realize how long it's going to take, how expensive it is, and how quickly it will be broken again it makes you think… "Am I the only one suffering this problem?", "What other solutions are available?"

This article will describe the problem and inform you about the depth of this simple, but persistent problem, on all types of Boeing fire handle lens caps, from the B737, B747, B757, B767, and the B777; possibly even on the newer designs coming from Boeing as well? Aircraft manufacturers seem to stick to a design for a long time.

The Use and Abuse of the Fire Handle

When something breaks we always like to find who's guilty, and to rectify the situation. In this case it seems that the guilty is more a sum of factors rather than a single cause. On the one hand we do have the crews, and it's easy to blame them, because they do break a lot of items in the cockpit due to the stressful situation, and in some cases a reckless attitude towards a simulator, most of the times rented, and certainly not their responsibility to take care of. So, yes, crews do break things more than often, so why not make them the prime suspect? Other than the flight crew there's the maintenance team, always under valued and on the spot for the management, that most of the time thinks they fix most the issues with a kick or a hammer. However, if this problem is appearing in so many other training centers, we have to assume that design or material are to blame — it always happens into a particular manufacturer or vendor of fire handles, and not to others, so certainly the design and materials used are a factor in the problem.

Why Do the Fire Handle Lens Caps Break?

The fire handle lens caps used on simulated Boeing aircraft break in one of two consistent ways: On the lens top face, due to the crew applying pressure pressure with their thumbs (wrong technique), instead of firm grab under the handle with four fingers and then a straight pull up; Another type of crack on the lens top is due to the sharp press the handles receive on the top to reseat them once the exercise is finished. At the same time it is quite common for the lens face lettering, indicating engine number (1, 2, 3, 4, or APU )  or the engine letter (L, R, or APU) to become eroded — this is once more due rough use. The other place that the lens caps break is the plastic clip on both sides of the lens, where it's inserted into the handle. This area, in theory, is only under stress when engineers replace the lamps or investigate a problem inside the cap and need to prise it open; but it is also under stress due to repetitive use of the handle, as these plastic clips are on the edge of the support when they're used.

All parts mentioned so far are aircraft parts, and are used on the simulator as originally fitted to the aircraft. The big difference comes in the amount of use these items get on the simulator in comparison to on the real aircraft.

How many times does a crew use a fire handle in real life operation? If we consider the average life of the aircraft we would have to say that you will never use these handles; but if you do use them, it will be once in the whole life of the aircraft, and certainly never all of them including the APU.  However, in a simulator these handles are used regularly. If we consider a busy simulator operating 20 hours a day, they could be used once per day by each crew — that is 365x5 or 1,825 times per year! When you consider the amount and diversity of training you could argue that they're used even more than that!

This first picture shows the status of a set of B737 fire handle lens caps after 4 years of use. Note that the lens cap for ENG#1 has no side clips; the APU lens cap has one side clip missing; and that the ENG#2 lens cap (shown including the lamp holder) has some paint missing from the lettering and both side clips are broken.

The second picture shows a lens cap from an APU fire handle with one good side clip and a one broken clip. Note the point where the clip has fractured.

The picture above shows an ENG#2 lens cap and lamp holder. The clip on this side is completely missing. Note the marks left by the repetitive use and removal of tape to hold the unit in place.

Above is an APU fire handle lens cap with a healthy plastic clip on this side; but where tape has been used to secure it, because the clip on the other side is broken, it has caused some of the paint to come off.

Who is Suffering from This Problem?

Is this only my problem, or are we all suffering from this? The evidence shows we are all in the same boat. Original replacements for these lens caps are expensive and in short supply (here is a business opportunity for all those 3rd party simulator suppliers). Delivery times are long, especially for those operators who don't have direct links with Boeing or who don't have direct supply from aircraft engineering logistics support groups. But it only affects the Boeing aircraft range, and only simulated Boeing aircraft.

Past References to the Problem

We are lucky, we still can dig into the past and see for how long this has been a problem, and how the problem has evolved. Lets have a look at the SimUser archives (at the time Simlink) and see what we can find , we will also visit the FSEMC archives and finally return to SimUser to look at the SimUser forums.

SimLink Archives

Simlink was the original SimUser, running since 2000 under egroups and then later on under yahoogroups. Simlink was a mailing list dedicated to simulator engineers and providing news, ideas exchange and participation to solve problems. http://www.yahoogroups.com/group/simlink

Aug 24, 2000

As a Simulator engineer we have to solve any problem by any possible way. Here I would like to share one of my experience with all the members of this group. In EVA AIR I have successfully develop a series of parts : "Fire Handle Switch Covers(Caps)".These caps used on B747-400 such as R, L, 1, 2 ,3 ,4 and APU Fire handle switch caps. Each cap costs around USD35-40/EA with non FAA Approval (for Sim. only). These caps are fully tested for almost 3 years,up to now the caps still working well. If any Airlines are interested in such parts, they could inquire a QUOTATION for a number of total Qty. It will cost down the price.

Jul 30, 2001

At last i found a place where you can get lens-cap for your Boeing fire handles , yes the lens cap that breaks quite often on the fire handles ,specially when trying to change the bulbs.

B747, B777 , B757 , B767 , engine and apu . If you have any other lenscap required and you can provide a sample they will made them , so customised designs are available for other switches if required (say B737 or MD ,...) . These lenscap are made for CPT and simulators at a much better price than the real thing , MTBF is the same or even better then the real thing . For details , pricing and qty required please forward your queries to  This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

I don't know how many people actually bought the parts or how many were sold, but I would like to insert in here photos received at the time of the parts being tested. The samples were originally for a B747.

The pictures above show the common problems of bending of the plastic clips and shrinkage of the plastic due to heat.

This pictures above show testing for heat problems: 24 hours with all lamps on using 387 filament lamps. Note that this example was for the B747 and has3 lamps powering the unit.

The FSEMC archives

It is later on, in 2004, when the subject suddenly appears at the Flight Simulator Engineering and Maintenance Conference (FSEMC). The annual reports from the FSEMC can downloaded from the ARINC Web site: http://www.arinc.com/fsemc. The following comments have been extracted from these reports:

FSEMC 2004 Conference  

MISCELLANEOUS - FLIGHT SIMULATOR SYSTEMS

Aircraft Parts O2 Masks Fire Handles: Question submitted by Alteon

O² masks and fire handles are generally aircraft parts used in simulators, but were never really designed for the high frequency of training. As a result, many simulator operators see very expensive repairs on these components since you often have to get aircraft repair shops to service these parts. We have found some repair shops that will price repairs lower due to our limited use of the part in a simulator. We would like to know if other operators have found a vendor who provides consistently inexpensive and reliable repairs for these parts, and if that vendor is equipped to handle all aircraft models and mask types.

Other user and vendor comments, please.

Value of Resolution: Reduce maintenance workload

SOBOL/PAIFA – It’s true that the aircraft parts are not robust enough for the day-to-day use they get in a simulator. We’ve taken many of those parts to a machine shop locally and had new parts manufactured, usually out of stronger materials. This includes fire handles, doors on the boxes for the oxygen masks, parking brake handles, etc. It will reduce the number of repairs, but even then, those parts don’t last forever. The machine shop makes the parts considerably cheaper than you can get the aircraft parts for. They may last four or five years instead of four or five months, but they still wear out. As far as the oxygen masks, we just buy a lot of the bit parts that go into the masks including the headband, microphone and hoses and repair them ourselves.

DOWLING/BRITISH AIRWAYS – We are currently evaluating repairing oxygen masks in-house. We’ve been looking at small repairs in the region of £1,000, which is getting a bit uncomfortable to live with in the current economic climate. We’ve had some success in locating a supplier who is able to give us components for a range of oxygen mask assemblies. One caution from our perspective is, we had great concerns about any components finding their way back onto aircraft. We’ve actually declared all our oxygen masks with a simulator suffix and marked them accordingly so this won’t happen.
It is possible and if I can be of any help, I can give information of the supplier we’ve just found.

MODERATOR - This question is closed

While there was specific mention of the fire handles in the question, the answer was more directed at a solution to the problem of the oxygen masks (this item deserves another article on its own).

We have to wait untill 2005 to see the question raised again, and a bit more information about the problem.

FSEMC 2005 Conference

PRODUCT SUPPORT

29 3rd Party Source Fire Handle Lens All B737: Question submitted by Southwest Arilines

Has any user had any experience using a 3rd party Fire Handle Lens?
We would like to know if they are more reliable, and if so, we would like supplier contact information.

Other user and vendor comments, please.

Value of Resolution: Provide Information

TEEL/SOUTHWEST – I have had a couple of users contact me who have pre-read this question. We used a manufacturer in Hong Kong.

WENIGER/WESTJET – I contacted the manufacturer in Hong Kong. I received a set of these a couple of years ago when I first looked into the issue. The lenses are okay, but they are rather fragile, and the tabs on must be specified exactly before manufacturing. I sent them back eventually because I was not satisfied.

GRAN/SAS – We did the same thing and we are using the lenses. The only advantage is that they are much cheaper, but they are just as bad.

LONGTIN/CAE – We’ve reviewed this question in a more detail with Dave Bingham from Southwest. They are experiencing a very high failure rate. I am assuming from the comments I have just heard that this is a general problem for Boeing fire handles.

I’d like to get a show of hands of the users who have lenses cracking, etc?

Okay, thanks. For your information, we did develop a prototype acrylic retainer a number of years ago that goes over the handle in order to absorb the pressure exercised on the lenses when you actually turn it. We have used this on one simulator at SAS, an FTD. Does SAS have any comments?

GRAN/SAS – Yes, we tried it, but they were not accepted by our pilots, so we had to take remove them.

LONGTIN/CAE – Is that due to the fidelity trade off because the form and fit is different? It obviously makes it a little bit bigger.

GRAN/SAS – Yes, they were a bit big and lumpy, and it was not the same form, fit, and function that the pilots are used to. We actually had the authorities present and they said, definitely no, the crews could not use it.

RHOADS/PLACARDS PLUS – I am a retired airline employee. We experienced many problems in this regard. One of our fixes to reduce the problem is to put LEDs in place on the original B737s. LEDtronics now makes an FAA-certified direct replacement. The only issue we had was on some simulators that used a driver with an open collector, the lights would glow dimly even though they weren’t fired, from a minimal current flow. We had to add a 1k resistor for each fire handle to load it down. The bottom line is this does reduce the times that you are going to have to push the tabs in to pull the lenses out. That is when the breakage occurs. Those handles are good. Another issue was that somebody else made a handle replacement, but the wires were always breaking. The bottom line is, if we can keep the pilots from getting in there and pushing on it, even with LEDs, you are going to reduce the problem. The fire pull handles are $500 each if you have to replace the entire item. It is not going to eliminate breakage. So in my mind, a replacement handle would be a better fix.

GRAN/SAS – We are using LEDs. Definitely, it helps a lot and very seldom do we have to go in there. Still, it’s the pilots that break the lenses—it’s not the technicians. Our solution is to use a very clear tape that is accepted by the pilots. It doesn’t look good, but it keeps the lenses in place. After using this, we haven’t had to change lenses.

PROMISEL/FEDEX – We have experienced lenses cracking and breaking until we traced the problem to the crew members. Once the instructors showed them how to pull the fire handle without using thumbs, it worked fine and we haven’t experienced any cracked handles.

WERNER/LUFTHANSA FLIGHT TRAINING – We also replaced this with LEDs, and we have not experienced the problem again.

SimUser Forums 

Lets have now a review of the SimUser Forums: http://www.simuser.com/. We now have a reasonable idea of the problems and solutions already implemented on some simulators, but we need to know if the problem still exists.

Mar 16, 2006, the problem appears again, but this time in the SimUser Forums. It is here that we can find the latest contacts to source the problem parts:

Topic: Need Fire Handle Lense Caps B747-400 http://www.simuser.com/joomla/index.php?option=com_smf&Itemid=47&topic=514.0

Kari – i am looking for someone who can supply fire handle lense duplicates for our simulator. I was in contact with someone from china (from thomsonbio) but I don't get any reply's from him anymore...!? There was a topic here whith his contacts but it seems to have disapeared...

ZFT – Contact John Spurr [ This e-mail address is being protected from spam bots, you need JavaScript enabled to view it ] He can help with Fire Handle lenses

Lausitzaviation – Look at http://www.simzation.com/ and contact boy bruin. He is producing fire handles for the 737. I think he can make lenscaps for the 747 too and the price is very affordable for the professional market.

LisaD – I just purchased them in Nov from ThomsonBio for $35.  I have sent an e-mail to see if he still makes them.  I have current email as This e-mail address is being protected from spam bots, you need JavaScript enabled to view it This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

Conclusion

1. Educate the crews, tell them to be carefull, to use the fire handles with care and to pay attention on how to pull them, and to push them back in place after the exercise.
2. Educate the engineers, they need to be careful as these parts are fragile and easy to break due to their design and the materials used. Take extreme care when you replace them or the lamps.
3. Replace the original lamp 387 with its LED replacement; any, FAA approved or not will do. This will allow the bulb to run for a higher number of hours, and at the same time reduce the heat on the plastic of the lens cap, in turn reducing the number of visits the engineers will need to make to replace the lamps. At a minimum this will reduce the number of times the cap will be at risk of being broken due to essential maintenance work.
4. Cover the caps with transparent tape to avoid the letters to be worn off in use; use the tape after the clips are broken and not before.
5. You can source the caps from your usual aircraft part supplier, but you do have an alternative supplier in the sources mentioned above.
6. Note some simulator manufacturers have already replaced the lamps with LEDs, improving the product, if it is not the case on your simulator contact the manufacturer and ask about it. It is quite possible that they already have the items and can provide you details.
7. If you are a business man with vision, this is an opportunity for you to come up with a replacement handle that manufacturers, and simulator makers, will be happy to buy, and replace on every Boeing simulator made, to save time and money. The simulated handle should be a direct replacement, and should cover both problems: the fragile lens cap; and the heavy use of the actual handle, and certainly come at a reasonable fraction of the original part cost.

Reference Data

Finally, the most eagerly awaited references and technical data; or in other words, the section engineers like us normally jump to, to get to the data we need the most:

B737 Fire Handle Lens Caps (from the IPC*)

ENG#1 lens cap PN : D533-04-205
ENG#2 lens cap PN : D533-05-205
APU#   lens cap PN : D533-06-205

If you want them with the bulb holder it's the same number just change the –205 at the end to –200.

* Note: If you have the PN for the other Boeing models I will be glad to include them in this article, please send them to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .

Lamp Sources

Original lamps used – PN: 387, replacement LED can be sourced at LEDtronics, Radio Spares (RS), Farnell, or from your simulator manufacturer.

RS – Components
http://www.rs-components.com/

RS PN for 387 T-1-3/4, Midget Flange, Single Contact 28V, 0.04A, Incandescent lamp:
2508325442; 2509288681; and 2508739021. The different part numbers represent lamps from different suppliers.

RS PN for LED replacement for 387 incandescent lamps: T1 3/4 min flange red multichip LED, 28Vdc:
585-680 (red); 585-703 (yellow)

Either the red or yellow LED versions can be pressed into service because they sit behind a red lens cap.

Pricing will vary by country. Lamps sold in packs of 10. 

Farnell – Components
http://uk.farnell.com/
Farnell PN for 387: 1139348, 3134660, or 653664.
Farnell PN for LED replacement: 1421648 (white); 1421934 (red). Vendor is Dialight Corp P/N 586-1106-105, and 586-6404-205 respectively.

LEDtronics
http://www.ledtronics.com/
This company is a leader in led replacement for lamps.

You can also check their avionics replacement LED lamp reference at:
http://www.ledtronics.com/datasheets/Pages/avionics_based_leds_chart/5.htm

PN for generic 387 LED replacement in several colours – see series F200-P.

Make sure you pick the 28V version. You can select different colours in case you want to use them for other locations.

PN for FAA approved replacement for 387 lamp: BSD-1884.

Also from LED tronics you can see a comparison between the MTBF of a normal filament lamp and the replacement LED. The table is for the FAA approved replacement:

The LED lamp will last 7 times longer that the incandescent lamp, or in other words, if used 24/7 will last for 5 years, whilst the filament lamp under the same conditions will not even reach a complete year! Heat to the lens cap is also almost halved with the LED lamp and the same applies to the power consumption.

Suppliers of Fire handle Lens Caps

Boeing (Genuine aircraft parts)
http://www.boeing.com/ and associated vendors.
Consult your IPC.

If you're not an aircraft operator you may have dificulties obtaining the parts directly from Boeing, so you could search for generic replacement items. 

Hot Shot Trading Company-Taiwan  (Simulated parts) (Updated 22-April-2009)
Contact by email to:  This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

A good choice for non-aircraft operators. Parts sold in sets with a minimum quantity of three sets. Pricing as of May 2008 was around $120 for the B737 sets, $150 for the 757/767 sets; and $250 for the B747 sets. Delivery time approximately two weeks from order receipt. The illustrations below show the the simulated lens cap. Contact This e-mail address is being protected from spam bots, you need JavaScript enabled to view it for more details and to order.

SimZation (Simulated parts )
http://www.simzation.com/, contact This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

The SimZation fire handles are not as aircraft form-fit-and-function replacements as found in top end simulators, but is a good alternative if the complete assembly is to be replaced, but it isn't suitable as a replacement for existing as-aircraft units fitted to a simulator.

Information Exchange

FSEMC: www.arinc.com/fsemc
SimUser: http://www.simuser.com/

Author

Antonio R.G. Pineda
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Any feedback about this article will be appreciated.
Any new sources or technical tips about this problem will be mentioned and references included. If there is any other topic you would like to see reflected on an article please do let me know.

Replacement Lens Caps Samples from HotShot Trading

Simulated Replacement B737 Fire Handle Lenses

Simulated Replacement B747 Fire Handle Lenses

Simulated Replacement B757/767 Fire Handle Lenses

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