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vertalop
21st Jun 2002, 08:33
I am a frequent passenger on a local airline's B737-400s. On the top surface of the engine fairing there is a four sided panel, the rear edge of which is in line with the rear of the slats. Looking out of the cabin window I often notice a number of missing screws around the edge of the panel. Can anyone tell me how many of these screws are permitted to be absent? Should I be considering getting off when a row of six are not present?:(
Whatever the manual says I have to tell you having missing screws on an engine panel clearly visible by the pax does not do a lot for passenger confidence!

wryly smiling
21st Jun 2002, 20:22
she's a big jet,she'll carry it or thats what I'll tell them at the board of enquiry:D

QAVION
22nd Jun 2002, 02:43
Chances are, vertalop, that the engineer who put on the panel was aware of the missing screws and the fact that they are missing will have been logged somewhere... The screws may not have been inserted due to, say, faulty anchor nuts. However, it is a common practice to circle the hole with a marker pen to make it more visible to the people who will repair the anchor nut later on when sufficient ground time is available.

Not being terribly familiar with the airplane type, it's difficult to make an assessment of the situation (As an engineer, I would need to look at the panel and assess whether it is a simple access panel or something which is load bearing and integral the airplane structure). To put you at ease however, Boeing has a tendency to put 4 times as many screws in panels than is necessary, so, odds are, your airplane was not in any danger.

By all means, however, please notify any discrepancy to the cabin crew... and allow the pilots/engineers to make a judgement on the safety of the panel. Also, if you see something in the cabin near your seat which is amiss, please report it, even if you have broken something yourself. Airlines don't make you pay for the damage... They are probably more likely to thank you for pointing it out, allowing engineers to fix the problem before the next flight... which means the next passenger will not be inconvenienced by the inoperative/broken item.

Rgds.
Q.

Checkboard
22nd Jun 2002, 04:17
Also, if you are viewing them from inside the aircraft, sometimes the top of the screw head looses its paint, and the head becomes a bit rusty. You may be looking at this - i.e. the screws are there, but they look like they are missing from a distance through a window when compared to the other screws that still have their paint.

Weight and Balance
23rd Jun 2002, 01:25
To follow up on part of Qavion's post:

I've pointed out apparent minor problems to the cabin crew three times in the last 20 years, and they always took it very well. (Big oil leak on a 737, crack in a fiberglass fairing that grew noticably during flight, and a quarter-turn on a SAAB 340 nacelle that popped out on takeoff.)

Of course, I don't know if they actually fixed anything afterwards....

lunkenheimer
24th Jun 2002, 22:01
There was the time I pointed out fuel seepage from an access cover on the wing of an MD-11. Took an hour for the ground crew to bless it with their ok. The captain told us slf that the seepage was normal. I was glad I did it, but my traveling companions weren't ...

Mebbe I should have waited until after take-off to mention it

lomapaseo
25th Jun 2002, 00:54
>There was the time I pointed out fuel seepage from an access cover on the wing of an MD-11. Took an hour for the ground crew to bless it with their ok. The captain told us slf that the seepage was normal. I was glad I did it, but my traveling companions weren't ...

Mebbe I should have waited until after take-off to mention it
<

Once while very young, I waited until landing to mention to the captain that my outer B727 window had cracked during the takeoff. The captain was not happy about my delay.

at least I got home on time.

Checkboard
25th Jun 2002, 02:00
There was the time I pointed out fuel seepage from an access cover on the wing of an MD-11. Took an hour for the ground crew to bless it with their ok. The captain told us slf that the seepage was normal. I was glad I did it, but my traveling companions weren't ...

You should then have sent up a note to the Captian pointing out that the other wing lacked the normal seepage! ;)

DoctorA300
25th Jun 2002, 19:51
Checkboard,
Next time you find a rusty screw on your walkaround, please tell your freindly ground engineer. :D :D :D :p steel dosnīt rust.
Brgds
Doc

Checkboard
26th Jun 2002, 03:47
G'day Doc,

Steel does rust, stainless steel is corrosion resistant. Haven't flown for eight months or so, but I do remember brown screw heads - call 'em dirty then :)

DoctorA300
26th Jun 2002, 19:26
Checkboard,
Sorry to hear you havnīt flow for 8 months.
To get into nitty gritty detail, Steel, Stainless or not dos corrode, most everything dose, but with Stainless 1804, which is what most aviation screws are made of, dose not go brow when corroding, It gets black and in patchs, but due to the size of a screw you wouldnīt notice the patches. The brown residue yoy have noticed on screwheads is most likley drie out grease or as you say yourself...dirt.
To get back to the original topic. Most commercial aircraft maintenance manuals of today allow approx 20% fastners to be missing from non stressed panels, as long as they are evenly spaced out.
Brgds
Doc

vertalop
3rd Jul 2002, 14:14
ASFKAP
Can I take that as a definitive answer for any engine panel on the 737-400...4 screws missing are permitted? These screws are counter-sunk and there is no doubt that they are missing, not just discoloured. Is there a part number or name for the exact panel as per my description above?

I will start counting! I am sure that I have seen more than that in the past. I will be sure to advise the crew in future!

Many thanks all.

vertalop
4th Jul 2002, 09:07
ASFKAP

Thanks. The panel is actually on the top surface of the wing, in line with the slats, where the engine mounting fairings(?) are. It is only visible from above, or the cabin window.

eng1170
5th Jul 2002, 02:21
sounds like the panel that covers the thrust control drum or the one aft of it that covers the join between the engine upper link strut and the wing surface. Infact reading back its probably the latter. The attach brackets underneath are only plastic along the trailing edge and these are very easy to break when the panel is off (trust me this clumsy fool has done it!!) and whats more to replace the bracket you need to access the inside of the fuel tank to get to the nuts on the bolts!!! If this has been broken it may not have been possible to repair at the time and be on a carry forward defect until the next hangar input where the fuel tank can be drained and access gained.

Just a thought!! (and yes I do work 737-400's!!):)

vertalop
11th Jul 2002, 07:24
eng1170
Thanks for your replies, but back to my original question...can you tell me if there is a maximum permitted number of missing screws in this panel?

eng1170
11th Jul 2002, 15:58
Hi Vert,

regarding your initial query I can only add what has already been mentioned in previous postings that there is usually a percentage permitted provided they are not all adjacent. The correct % seems to vary - I was always under the impression it was 10% but some of the other posts reckon it may be more or less, I don't know who is correct and have never actually seen this in "black and white", but as already mentioned there will be panels where there is no missing fasteners permitted and probably others where there may be more than the normal % allowed.

I will ask around our Tech. dept (some very knowledgeable people in there!!) and have a look through the DDM/MEL for the 73-400 as well as the SRM and AMM's as I would like to find out for my own info as well.

Thanks for reply and Happy Flying! Grae

spanners
12th Jul 2002, 13:43
Exactly where does it say that a pecentage of screws are allowable to be missing?
As said in the post above, the DDG gives info on missing panels but not on fastners on those panels.
I think that the old 10% stuff is a bit of an engineering urban myth.

Regds:D

eng1170
17th Jul 2002, 14:00
Hi guy's
Following a quick browse through manuals in the hangar I can refer you to 737-400 Structural Repair Manual ref 51-10-05 pages 1 to 12 which give general instructions to make it possible to operate aircraft with fasteners missing in secondary structure.
To quote from the pages secondary structure includes fairings,trailing edge panels, and access panels (further info found in SRM51-00-04). The missing fasteners must be of the type that are easy to remove such as bolts and screws, i.e not solid rivets.
Certain conditions apply before allowing the a/c to be dispatched i.e no fasteners must be missing from the leading edge of the panel in question, no fasteners must be missing from the corner locations, all fasteners must be installed on sides of panels that have 8 or less fasteners AND one missing fastener in 10 is permitted on a side but not on a leading edge of the panel.
Electrical or grounding fasteners MUST be installed.

The above is only part of the 12 pages in the SRM and it goes on to give further info and drawings as to where no fasteners at all are allowed to be missing and also further restrictions/limits as to where and how many there can be missing. Also included on page 5 is the inspection criterea for any missing fasteners.

Hope this is of some more help and I would recommend reading said references in the SRM for full info and drawings if you can get access to these. If not drop me an e-mail and I'll see if I can be of more help.

All the best - Eng