View Full Version : Metal strips above airliner's doors.

16th Jul 2002, 20:02
Does anybody know what the thin metal strips are for above the main doors on airliners. As a Boeing driver, mine has them, as does the 777, A320 etc.

I presume they are for directing the air around them, as they angle up at the front, and down at the back. Do they reduce noise or something?

The strip is u shaped from thin metal, with one edge attached to the fuselage.

Hew Jampton
16th Jul 2002, 20:04
Rain gutters.

16th Jul 2002, 20:06
would you rather get dripped on?


16th Jul 2002, 20:16
ohhhh!! That simple hey? :o :o Oops!
Here's me trying to think of some high-brow aerodynamic reason for them!! :) DOH!
Don't look very aerodynamic to me!!

Retires to a distance, slightly embarrassed.......

17th Jul 2002, 03:04
"Subsonic hydrodynamic flow directors"

"rain gutters" is such a coarse description;)

17th Jul 2002, 04:23

Lomapaseo, you might be on to something here. :):) After all everything in aviation must have an acronym.


17th Jul 2002, 11:49
quote - "As a Boeing driver"
quote - "what the thin metal strips are for above the main doors on airliners"

does this scare any other passengers reading this ???? :)

Young Paul
17th Jul 2002, 11:59
There are no stupid questions, only stupid answers. ;-)

It's not sufficiently technical for anybody to bother explaining it to the pilots during TR training. Until you've seen them working - on a rainy day off-pier, it's hard to imagine what they are for.

17th Jul 2002, 13:35

They also don't mention that the big, black wheels under the wings are supposed to rotate. Doesn't that worry you too?

Some things are considered either self evident or simply irrelevent. :rolleyes:

Flight Detent
17th Jul 2002, 16:31
He obviously doesn't have a Flight Engineer aboard.
Just imagine what else he is unsure of, but is to embarrassed to ask!

17th Jul 2002, 18:00
How can they rotate; they're flat on the bottom.:D

17th Jul 2002, 18:24
As someone said, Boeing flight manuals are strictly on a 'need to know' basis. I guess the type rating would take about 3 times as long if we knew everything about everything. Pilots know a little about a lot, if you know what I mean. I certainly had to learn a lot of different stuff, from how a jet engine works, to the toilet flush motor!! Saying that, I think it says it all that the chapter on our engines is about the smallest in the book.

I love the way that there is actually a big arrow pointing forward on the thrust lever quadrant saying 'Increase Thrust' - Duh!

17th Jul 2002, 22:21
sorry guys, was meant to be a little lighthearted :(

far be it from me to mock an airline pilot, and I do mean that, its my dream job

I'll slip back into the shadows ! :(

17th Jul 2002, 23:06

so THAT'S why they don't mention the wheels! Dohhh!!

And here I was thinking that the 'thump....thump....thump...' was just me getting the nosewheel on the centerline lights...:p

17th Jul 2002, 23:49
Is Tech Log always this funny? Blimey, if it's actually meant for really stupid questions, maybe I'll start posting... :)

22nd Jul 2002, 13:50
Back in the "Good Old Days", when we were expected to know "everything", like every hole in the cowl, bump and fitting, tyre pressures etc ( Yep, even pilots).

Picture very senior Captain, having just completed a differences course from the early 707, to the -320 series.

Very junior Training Captain, as we walk to the aircraft for the base training, pointing to a NACA vent for one of the ignitors cooling air supply, asks: " Wot's that".

The VSC reply was " I know that , wait, I remember, its on the tip of my tongue, just a minute, yes, that's a Boeing 707".

That was the end of silly and meaningless questions for the day.

Pitty he wasn't asked other standards, such as "How many holes in the overhead speaked face?" or "How many zeros on the DME indicator drums", the reply would have been well worth waiting for.

Tootle pip !!

23rd Jul 2002, 03:30
Just to add:

The angle of the rain gutters is dependent on the airflow at that point on the fuselage (so that when the aircraft is flying at high speed, it offers the least amount of drag). This is why some slope down and some slope up ;)


23rd Jul 2002, 10:13

You're having a laugh, aren't you?!! They ALL slope down, or they wouldn't be much good at getting rid of water, would they?

Talking of silly questions, anyone else heard of the SLF who couldn't understand how an aircraft could get moving on an icy taxiway. "Surely the wheels will spin?" he said!:D

23rd Jul 2002, 12:22
This actually happened when a senior captain converted to the L1011, Tristar from another jet, during the walkround:

Check Capt., 'How many fan blades are there on an engine?'

Senior Capt., 'Don't know, but if one is missing I reckon I'll spot it'!

23rd Jul 2002, 17:54
So lets see...These natty little rain gutters stop the water dripping on your head when you exit the plane onto the steps. Nice idea so far. Then you go down the steps and dash accross the apron to the bus in the pouring rain. Humm, perhaps they need to be a bit bigger.

23rd Jul 2002, 18:07
"What size particles can be removed by the pneumatic system filters?"

"Gee, I dunno."

"The answer is 40 microns."

"Oh. How big is a micron?"

"Ahh..I don't know."

"Why do you want me to know how big 40 of the f*****s are?"

24th Jul 2002, 07:33
Please don't think aeroplanes are designed for the comfort of passengers. The gutter is to stop the inside of the aeroplane getting wet, not to keep the passengers dry.

24th Jul 2002, 14:53
Rain gutters? I always thought they were for attaching a roof-rack... :rolleyes:

24th Jul 2002, 17:21
A roofrack... boy, till today I never could answer the Trainer Captains question of where to stow my ski's for winter holiday.

How many holes are there in the static ports? How many electric dischargers are attached to each wing? What is the use of the tiny blue + signs in the A320-cockpit?
I was asked those questions only a year ago, so much for the good old days!


27th Jul 2002, 10:48
There's nice to know, need to know and F knows.:)

Bally Heck
10th Aug 2002, 16:18
So does anyone know why there is a gutter on a B757, just forward of the potable water access hatch, on the belly of the aircraft?

10th Aug 2002, 16:31
Bally old boy, you’re gonna have to stop doing the walk round underneath the aircraft.

Get out in the rain like the rest of us.:D

Golden Rivet
10th Aug 2002, 19:54
Nice one Bally

No idea, but now I'd like to know !

11th Aug 2002, 01:49
OK, how is this for a guess BH:

When aircraft is flying in rain/cloud etc. water collected around the potable water access hatch and froze, lump of ice gets bigger and bigger until it falls off and falls through someones roof/head etc. also, on arrival at destination access hatch may be frozen solid and turnround time considerably extended whilst ice is chipped off/melts.

Solution: Put in a rain gutter that directs water away from access hatch and prevents ice forming?

Flight Safety
11th Aug 2002, 08:14
Gee, what's with you guys!

Imagine this OK. ;) ;) ;)

The fuselage is like very round OK (as in "circular") in cross section (that's like a big slice of sausage, get the picture?).

Ok, now when it rains, where does the water go that lands on top of the airplane? It like goes AROUND the "circular" fuselage, as in sticking to the side, flowing down, running down, in like little riverlets of little water streams.

Ok, now imagine in the rain that the skybridge is at the gate, it's slowly being moved toward the door, slowly pressing in, slowing surrounding the door. Now imagine if the little rain gutter wasn't there. It would be like walking through a little waterfall to enter the plane's door, from the little riverlets of rain water flowing down and around the side of the plane. You can see this right? :eek:

Now for the 757, "potable" means "fit to drink". Imagine the little riverlets of rain water, flowing down and around the fuselage, running into the hose connections while loading the drinkable water. It would be like, you know, getting the water off of your car after you washed it, into your canteen. :D :D :D

Gee you guys.... ;) ;) ;)

G-SPOTs Lost
11th Aug 2002, 09:35
As for daft questions:

Picture this, very respected, very well spoken ex BA 747 Flight Engineer teaching pressurisation and aircon at a ground school thats now skint.

For nearly four days the guy is going on about low and high pressure bleeds from the BRT, imagine all students frantically looking through their notes and index's for any mention of BRT!

BRT this, BRT that, for four full days.

Cause of massive discussion at lunchtime and over coffee, nobody wants to ask even though we are all desperate to know.

On the last day somebody asks the question

"Big round thing" comes the reply in this wonderful BA accent - whole class was pissing themselves for hours !!:D

Golden Rivet
11th Aug 2002, 09:48
Potable water panel Gutter strip - my theory

Have a careful look at the belly area of a 757 aft of the main gear and you will invariably find a hydraulic fluid leak eminating from the centre hydraulic pumps.

Couple this leakage with the crap off the main gear and you have a rather unsavoury mix.

This fluid streaks down the centre of the fuselage and is redirected around the potable water service panel by the gutter strip, thus keeping the connections clean and skydrol free.


Just an other number
11th Aug 2002, 11:56
Yes well that's very useful
a BRT is a big round thing
us amateurs want to know -
What's a big round thing?
We deserve to be told.

Golden Rivet
11th Aug 2002, 12:23
BRT = Engine ( Big round thing )

Capt Claret
13th Aug 2002, 16:10

Your answer seemes emminently sensible and I was mindful of it yesterday whilst eating lunch, and looking at the starbord side of an A340.

If I can remember correctly, the door just forward of the wing and the overwing exit both had gutters which sloped down towards the front of the aircraft. I imagine that at a slight nose up attitude (cruise ?) this would have made the gutter close to parallel with the airflow.

The gutter above the aft service door however sloped down towards the rear of the aircraft, thus a small nose up attitude would have increased the amount of drag (negligible I know) from this gutter.

Any thoughts on why this is so? :confused:

Flight Safety
13th Aug 2002, 17:07
Capt Claret,

I believe that sloping rain gutters above doors are more effective at diverting water than gutters mounted parallel to the ground. They simply drain water faster. You'll notice that most all rain gutters above doors on airliners are sloped.

Young Paul
13th Aug 2002, 22:13
... yes, in line with airflow when airborne. Oh, we've said that, haven't we?

Capt Claret
14th Aug 2002, 02:00
Flight Safety

Understood, I think I've perhaps been misunderstood, or, I've misunderstood.

Qavion said: The angle of the rain gutters is dependent on the airflow at that point on the fuselage (so that when the aircraft is flying at high speed, it offers the least amount of drag). This is why some slope down and some slope up

My question to Qavion is why would gutters on the same side of the fuse, slope different ways, two down to the front, one down to the rear.

I understand the need for the slope when on the ground.

Young Paul
14th Aug 2002, 11:01
Because that's the direction of the airflow. In front of the wing, the airflow goes up as it goes aft, to get over the wing. Behind the wing, it goes down as it goes aft, because the air is lower pressure behind the wing.

Golden Rivet
14th Aug 2002, 12:18
Cant believe it makes the slightest difference in performance if the slope of the rain getter is up or down !

Have a look at the CDL just to see how many bits may be missing on the airplane with 'negligible' performace penalty.


Flight Safety
14th Aug 2002, 20:37
I guess it makes sense that once a design decision is made to slope the rain gutter for good drainage while on the ground, to then fine tune the slope so that it offers the least amount of drag while in flight.

Young Paul
15th Aug 2002, 09:43
Suppose the fuel cost is 1kg per sector. That's (short haul) 2000 kg per year- several hundred pounds.

Just because you can't measure it doesn't mean to say it isn't there. Otherwise they wouldn't bother cluttering the aircraft up with all the CDL bits and pieces in the first place.

1 of many
15th Aug 2002, 19:33
Aren't the doors supposed to be closed in flight? If so does it matter where the drips go (not the ones inside)?

Beats me . .

Final 3 Greens
19th Aug 2002, 22:01
EGLD asks if this thread scares the pax .... well, not as much as the thread about forward slipping a 738...... (speaking personally)