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juantrippe
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So-Called "Gravel Kit" On 737s

Wed Jun 01, 2011 2:12 pm

Does anyone remember the so-called 'gravel kit' on B-737-200s. It was an attachment to the front landing gear and meant to allow for takeoffs and landings on rough terrain. I am pretty sure Alaska used them at one time. I am trying to get a pix of one and figure out how much additional weight it added to the landing gear retraction mechanism.
 
chieft
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 01, 2011 2:23 pm

Voila:

http://i237.photobucket.com/albums/ff249/jungle375/DSC_0491.jpg


Basically it comes with several parts:
a) The nose gear has a plate attached ("ski look"). This is to deflect any gravel etc that the nose gear kicks up, protecting both the underside of the fuselage and the engines.

b) The nose gear wheel well is modified to make room for the deflector to retract into.

c) The engines have vortex dissipators installed. These are basically tubes under the engine intake that direct bleed air to prevent vortices that would normally suck gravel and whatnot into the engine.

[Edited 2011-06-01 07:28:08]
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c172akula
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 01, 2011 2:27 pm

Some more info on the gravel kit here:

http://www.b737.org.uk/unpavedstripkit.htm
 
DaBuzzard
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 01, 2011 5:00 pm


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Photo © Michael Durning
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Photo © Jason Pineau



Couple of examples out of the database, no idea on how much extra weight the gravel kit added.
 
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HAWK21M
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 01, 2011 5:28 pm

I remember those fittings of the B732s.I doubt very many Unpaved strips used for Landing these days though.very Interesting concept.
although I wonder if a NLG Heavy impact would have damaged the Gravel protector.
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canoecarrier
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 01, 2011 6:07 pm

Quoting HAWK21M (Reply 4):
I remember those fittings of the B732s.I doubt very many Unpaved strips used for Landing these days though.very Interesting concept.

I don't any of my AS 732-combi photos here at work, I may be able to post one later. Either way, when AS switched over to the 734-combi a fair amount of government money got sprinkled around Alaska to pave the airports with gravel runways served by AS.
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AA737-823
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 8:10 am

I work on gravel kitted 737-200s every day.
There were more modifications that the list above included, starting with gravel deflectors on the main gear as well. They're not particularly visible.
The main gear wheel well also had some protective screens, but these were removed.
The lower red beacon was also retractable, but this has also been eliminated in favor of a wire mesh guard which does virtually nothing at all, but is not prone to failing in the 'up' position.

The ski adds a bit of weight, but it's not horrible. It's a two-person lift item, so to speak, but that's mostly because of size. I'd give it 100 pounds or so, not really sure.

Quoting HAWK21M (Reply 4):
I wonder if a NLG Heavy impact would have damaged the Gravel protector


Not horribly, in my prediction. It's spring loaded, which helps to deploy the gear should the crew have to revert to manual extension. But seeing as it's on four stout springs, it has quite a bit of give to it.
Changing nose tires, on the other hand, is a complete nightmare...... hate it.
And when you're landing on gravel runways, tires get changed at an inconceivable rate.

Any other questions, PM me....
 
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Starlionblue
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 8:18 am

Quoting AA737-823 (Reply 7):

The ski adds a bit of weight, but it's not horrible. It's a two-person lift item, so to speak, but that's mostly because of size. I'd give it 100 pounds or so, not really sure.

I think the main penalty is more drag from the enlarged gear well.
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HAWK21M
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 10:22 am

Quoting AA737-823 (Reply 7):
There were more modifications that the list above included, starting with gravel deflectors on the main gear as well. They're not particularly visible

Any pictures?.

Quoting AA737-823 (Reply 7):
hanging nose tires, on the other hand, is a complete nightmare...... hate it

I would think so.......

Fantastic Information shared there....Thanks a lot.
I may not win often, but I damn well never lose!!! ;)
 
canoecarrier
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 9:15 pm

Quoting AA737-823 (Reply 7):
The ski adds a bit of weight, but it's not horrible. It's a two-person lift item, so to speak, but that's mostly because of size. I'd give it 100 pounds or so, not really sure.

How easy is it to hook a tow bar up to a ski fitted 732? That can't be easy either.

Quoting Starlionblue (Reply 8):
I think the main penalty is more drag from the enlarged gear well.

I seem to remember hearing that having the ski on lowers the landing gear extension speed from around 230 to 180 knots.

Quoting AA737-823 (Reply 7):
Changing nose tires, on the other hand, is a complete nightmare...... hate it.
And when you're landing on gravel runways, tires get changed at an inconceivable rate.

What airports are they flying into that are still gravel? These have to be oil company charters to the north slope?

Great info there, thanks for posting.
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B6JFKH81
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 9:30 pm

What is the item attached to the engine in reply #3 and what does it do? I can understand the extra stuff for the wheels, wheel wells, beacon light, etc., but I'm really trying to understand what the purpose of that thing on the engine is  

Oooops, nevermind. The website from Reply #2 has some info:

"Vortex Dissipators
Prevent vortices forming at the engine intakes which could cause gravel to be ingested by engine. These consist of a small forward projecting tube which blows pressure regulated (55psi) engine bleed air down and aft from 3 nozzles at the tip to break up the vortices.
The dissipators are operated by a solenoid held switch on the overhead panel which switches off on a squat switch so that climb performance is not affected. (Similar to the wing anti ice switch on 3-900 series)."

[Edited 2011-06-02 14:33:19]
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yeelep
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 9:36 pm

Quoting B6JFKH81 (Reply 11):

Vortex dissapator. It takes engine bleed air and blows it were a vortex would originate, thereby preventing it.
 
DaBuzzard
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 10:54 pm

Quoting canoecarrier (Reply 10):
What airports are they flying into that are still gravel?

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Photo © Jason Pineau



Snap Lake (CSKB) NWT at least (charter afaik).
Last time I was there (about 4 years ago) Resolute Bay (CYRB) was still getting them as well.

I'd bet there are more given the distinct shortage (and short lifespan) of pavement in the Arctic  
 
canoecarrier
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 02, 2011 11:06 pm

Quoting DaBuzzard (Reply 13):
Snap Lake (CSKB) NWT at least (charter afaik).
Last time I was there (about 4 years ago) Resolute Bay (CYRB) was still getting them as well.

I'd bet there are more given the distinct shortage (and short lifespan) of pavement in the Arctic


Ok, well I should have specified in Alaska. But, I've spent a lot of time in Canadian bush planes interesting information none the less. Isn't Inuvik's runway paved, that's much further north than Snap Lake? Either way, you're right about the short lifespan of pavement in the Arctic.

Last I checked the Canadian-based operators of gravel kitted 737s were Air Inuit, Air North, Canadian North, First Air, and Xstrata Nickel.

[Edited 2011-06-02 16:17:09]
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Viscount724
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RE: So-Called "Gravel Kit" On 737s

Fri Jun 03, 2011 2:49 am

Quoting DaBuzzard (Reply 13):
Last time I was there (about 4 years ago) Resolute Bay (CYRB) was still getting them as well.

732s haven't served YRB for a few years on scheduled flights but there may still be the occasional charter.

If not mistaken, the only remaining point in Canada with scheduled 732 service with a gravel runway is Cambridge Bay (YCB). However those aircraft also operate many charter flights to remote mine sites with gravel strips.

Canadian North 732 combi landing at Cambridge Bay, population about 1,500. Gravel runway 5,076 ft.
http://www.youtube.com/watch?v=z-8OIEPB9ZE

1972 Boeing video of a 737-200 with the gravel kit landing and taking off from a grass runway at Hope, British Columbia (about 90 miles east of YVR).
http://www.youtube.com/watch?v=aOpBXmqa0eY
 
canoecarrier
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RE: So-Called "Gravel Kit" On 737s

Fri Jun 03, 2011 3:55 am

Quoting Viscount724 (Reply 15):
If not mistaken, the only remaining point in Canada with scheduled 732 service with a gravel runway is Cambridge Bay (YCB). However those aircraft also operate many charter flights to remote mine sites with gravel strips.

I'd think they keep the gravel kits around for charter ops. And, given where they operate between flying food and supplies they'd keep busy. I think Air North put their turboprop on the unimproved airports for passengers. But, last time I checked they put the HS 780 on the northern routes. Xstrata Nickel only had one 732 a year or two ago. but I'd wager they fly it to the mineral areas a fair amount.
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JETPILOT
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RE: So-Called "Gravel Kit" On 737s

Mon Jun 06, 2011 8:43 am

The DC-8 50/61 series also had blow away jets installed on the intakes to keep FOD from getting sucked up. You had to turn them off on takeoff.

[Edited 2011-06-06 01:45:03]
 
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longhauler
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RE: So-Called "Gravel Kit" On 737s

Mon Jun 06, 2011 2:40 pm

Quoting canoecarrier (Reply 10):
How easy is it to hook a tow bar up to a ski fitted 732? That can't be easy either.

It's funny you should mention that. On occasion, the "Combis" we flew were converted to all passenger on weekends and we did southern charters with them. This was done, as the normal B737-200s in our fleet were J/Y equipped, but when a Combi was converted to passengers, it was all Y, perfect for southern destinations.

But ... our Combis were also gravel kit equipped, so quite often we encountered a station that did not have the proper tow-bar, as the tow-bar was unique on the gravel kit equipped aircraft.

As a result, these were the only times in my B737-200 career that I had to do a power-back, as we had no other choice.
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HAWK21M
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 09, 2011 6:34 pm

Quoting longhauler (Reply 18):
But ... our Combis were also gravel kit equipped, so quite often we encountered a station that did not have the proper tow-bar, as the tow-bar was unique on the gravel kit equipped aircraf

How different is the towbar attachment to the NLG.Any pics?.
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AA737-823
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RE: So-Called "Gravel Kit" On 737s

Tue Jun 14, 2011 6:59 am

Quoting HAWK21M (Reply 19):

Not sure about the above story, but at my carrier, we use the same towbar for 737-200, 737-200 gravel, and 737-NG operations. The tow fitting on the nose gear is about a half inch lower on the gravel airplane, but is otherwise identical. No clue why one would have to power back...
 
yeelep
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RE: So-Called "Gravel Kit" On 737s

Tue Jun 14, 2011 11:18 am

At my carrier, we also had towbars specific to the gravel kitted -200's. They could be used on all the 737 models, but nobody did because they were a bulky, heavy pain in the ass. The towbar we use on all other 737's are about a third of the weight, easy to maneuver and likely much cheaper.
 
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longhauler
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RE: So-Called "Gravel Kit" On 737s

Tue Jun 14, 2011 1:16 pm

Quoting AA737-823 (Reply 20):
No clue why one would have to power back...

Actually, ironically (looking at your name) it was only at the American Airlines handled stations to which we flew. Looking at my log book, (I keep track of unusual things like powerbacks), I see I did a powerback at MCO, DFW, LGA and MIA ... all AA handled stations. All were in combi/gravel equipped B737s.

The ground handing comments were always the same, "We don't have a tow bar to fit that nose wheel". I just shrugged, it is their domain, I just fly them!
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
KELPkid
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RE: So-Called "Gravel Kit" On 737s

Tue Jun 14, 2011 3:19 pm

I've been wondering about the title of this thread since it started...the gravel kit isn't "so called", it exists and it does what it purports to do  
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AA737-823
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 15, 2011 12:10 am

Quoting longhauler (Reply 22):
Actually, ironically (looking at your name) it was only at the American Airlines handled stations to which we flew.

I am in no way associated with American Airlines.... though when I was a young'un and first got my username here, I hoped to be when I grew up!

Quoting longhauler (Reply 22):
The ground handing comments were always the same, "We don't have a tow bar to fit that nose wheel". I just shrugged, it is their domain, I just fly them!

Well, I see two possibilities: either they were ignorant that the design is different, or... my company just has the one towbar style, and we use it on all birds. But you can tell by looking at the two gear hookups that there's very similar.

Quoting KELPkid (Reply 23):
I've been wondering about the title of this thread since it started...the gravel kit isn't "so called", it exists and it does what it purports to do

If it's nits you'd like to pick, then I'll go ahead and point out that it isn't called the gravel kit at all. It's officially known as the "Unimproved Landing Surface Kit." So there- go find another nit.

[Edited 2011-06-14 17:11:25]
 
canoecarrier
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RE: So-Called "Gravel Kit" On 737s

Wed Jun 15, 2011 1:54 am

Quoting AA737-823 (Reply 24):
Well, I see two possibilities: either they were ignorant that the design is different, or... my company just has the one towbar style, and we use it on all birds. But you can tell by looking at the two gear hookups that there's very similar.

I think I'd stop short of saying they were ignorant. Gravel kits aren't exactly that common south of the border. Here you have a Canadian telling you a story about flying south to places like DFW with a ski fitted 732, it's not exactly like they grow on trees in Texas.

There are a lot of ways to tow a plane, I wouldn't put as much faith in the ground crew that Longhauler did, I could see someone rolling up in one of those scissor lifts ripping off the ski. Pitty none of my photos of flying around Alaska or the Yukon show the ski or the towbar. I even looked.
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juantrippe
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RE: So-Called "Gravel Kit" On 737s

Thu Jun 16, 2011 9:26 pm

To AA737-823

DId you say the total weight of the gravel kit is about 100 lbs? or was that the weight of only one component?

I am trying to figure out how much addittional demand the gravel kit puts on the wheel retraction mechanism. Any idea?
 
AA737-823
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RE: So-Called "Gravel Kit" On 737s

Tue Jun 21, 2011 10:11 am

Quoting juantrippe (Reply 25):
DId you say the total weight of the gravel kit is about 100 lbs? or was that the weight of only one component?

Just the ski.

Quoting juantrippe (Reply 25):
I am trying to figure out how much addittional demand the gravel kit puts on the wheel retraction mechanism. Any idea?

I have no idea. I suspect there's quite a substantial amount of drag, because for some time, the ski is perpendicular to the airflow. The ski itself has its own hydraulic actuator, to help position it for easy retraction.
But I do know that the time limit for NLG retraction and extension WITH the ski is six seconds. I seriously doubt, however, that there are very many out there that can accomplish such a feat in six seconds....
 
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longhauler
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RE: So-Called "Gravel Kit" On 737s

Tue Jun 21, 2011 12:49 pm

Quoting juantrippe (Reply 25):
I am trying to figure out how much addittional demand the gravel kit puts on the wheel retraction mechanism. Any idea?

It is going back about 10 years, but I do recall VLo was around 180 knots. And even 150 knots with some hydraulic failures. (I don't recall which). So it much have been pretty taxing on the system.

I do recall it was very restrictive, and you had to plan your approach well. To remind you, there was a small "ski" attached to the gear handle ... just in case you forgot on a dark dirty night.
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