rikkus67
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Gravel Deflectors & 737NG / Other Newer?

Mon Jan 26, 2009 10:58 pm

I noticed today a great close-up photograph posted of the 737-200 nose gear gravel deflector plate, and it got me to thinking:

Why wasn't the gravel deflector adopted to newer 737's, and is there ANY other (non 737-200)aircraft flying that uses this technology?


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Viscount724
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RE: Gravel Deflectors & 737NG / Other Newer?

Mon Jan 26, 2009 11:14 pm

The nosegear gravel deflector is part of a special gravel runway kit offered by Boeing on the 737-200 (most were 737-200C combis with main deck cargo door). That kit also included bleed air nozzles at the front of the engines to deflect debris that might otherwise be ingested into the engines, heavy duty brakes/tires, special Teflon coating on the lower fuselage/wings to reduce damage from flying stoes, and a retractable lower rotating beacon (retracted on takeoff/landing to prevent breakage by gravel).

There is no need for that equipment on aircraft that operate on paved runways. Several of those 732Cs with the gravel runway equipment still operate in northern Canada wherea some runways aren't paved. They also operate charters to mine sites etc. with gravel airstrips.

I doubt there was any demand for that kind of equipment on later 737 models. AS had that equipment on 732C combis (now retired) at one time, but I think they eventually removed it as they were no longer operating to any airports with unpaved runways.
 
71Zulu
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RE: Gravel Deflectors & 737NG / Other Newer?

Mon Jan 26, 2009 11:22 pm



Quoting Rikkus67 (Thread starter):
Why wasn't the gravel deflector adopted to newer 737's, and is there ANY other (non 737-200)aircraft flying that uses this technology?

I guess the larger intakes of the CFMs used on the -300s and up would have made it hard to keep the debris out. Did the 727 offer some version of the gravel kit (obviously without the vortex generators)?

Here is some more info:

http://www.b737.org.uk/unpavedstripkit.htm
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HAWK21M
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RE: Gravel Deflectors & 737NG / Other Newer?

Mon Jan 26, 2009 11:48 pm

This was only on the B732s due to the surface they operated on.

Quoting Viscount724 (Reply 1):
Several of those 732Cs with the gravel runway equipment still operate in northern Canada wherea some runways aren't paved

Any reason in todays times,why the runways would not be paved,this will unnecessary reduce tire life.
regds
MEL
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71Zulu
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RE: Gravel Deflectors & 737NG / Other Newer?

Mon Jan 26, 2009 11:54 pm

Some of these operate to mines and oil fields where there is no paved runway and maybe will never be. Also some operate off of ice runways where you can still have debris and chunks of ice and snow getting to the engines.
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Viscount724
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RE: Gravel Deflectors & 737NG / Other Newer?

Mon Jan 26, 2009 11:57 pm



Quoting 71Zulu (Reply 2):
Did the 727 offer some version of the gravel kit (obviously without the vortex generators)?

Not sure what special equipment they may have had (can't recall anything like the nosegear deflector), but 727s have definitely operated off gravel runways. Photo below taken sometime in the 1970s of a 727-100C combi operated by former Canadian regional carrier Pacific Western (which merged with CP Air in 1987 to form Canadian Airlines) at Resolute Bay (YRB) in Canada's Arctic, 74 deg. N, 922 nm from the North Pole. YRB has a 6,500 ft. gravel runway.

http://www.pwareunion.com/images/Aircraft/B727-YRB.jpg
 
Viscount724
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RE: Gravel Deflectors & 737NG / Other Newer?

Tue Jan 27, 2009 12:04 am



Quoting HAWK21M (Reply 3):
Any reason in todays times,why the runways would not be paved,this will unnecessary reduce tire life.

I expect one reason is the huge temperature variations from summer to winter (e.g. from approximately +25C to -50C) which would make paved runways prone to cracking and a lot of maintenance. The few communities with scheduled service that still have unpaved runways are also very small (some with a population of just a few hundred) so there would also be a cost factor. Runways at larger towns in that area are paved.
 
MrChips
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RE: Gravel Deflectors & 737NG / Other Newer?

Tue Jan 27, 2009 3:32 am



Quoting Viscount724 (Reply 6):
I expect one reason is the huge temperature variations from summer to winter (e.g. from approximately +25C to -50C) which would make paved runways prone to cracking and a lot of maintenance. The few communities with scheduled service that still have unpaved runways are also very small (some with a population of just a few hundred) so there would also be a cost factor. Runways at larger towns in that area are paved

Those are some good reasons, but the biggest reason why most runways in Northern Canada are unpaved is because of the permafrost. In case you're wondering what permafrost is, it's exactly what it sounds like - the soil (and even the underlying rock) is mixed with ice that never melts.

A paved runway will absorb a large amount of heat from the sun (even at these high latitudes), and in turn melt the permafrost underneath it, causing the runway to literally break apart after a few years. Of course, it is possible to build a paved runway that will not melt the permafrost, but it would be prohibitively expensive, even for a large center.
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CanadianNorth
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RE: Gravel Deflectors & 737NG / Other Newer?

Tue Jan 27, 2009 2:08 pm



Quoting MrChips (Reply 7):
but the biggest reason why most runways in Northern Canada are unpaved is because of the permafrost



Quoting Viscount724 (Reply 6):
The few communities with scheduled service that still have unpaved runways are also very small (some with a population of just a few hundred) so there would also be a cost factor.

Both are correct really. Permafrost is the big reason, but also there is the factor that for a community of only a few hundred that only has a couple flights per week, there's just not enough usage to justify the costs.

And as for the original question, I believe ground clearance issues with the CFM engines are the main reason for the gravel kit only being available on the 737-100/200. I could be wrong however.


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JAGflyer
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RE: Gravel Deflectors & 737NG / Other Newer?

Tue Jan 27, 2009 4:20 pm

While we're discussing unpaved runways, Indian Airlines has special A320s with double bogie main gear (4 wheels on each gear instead of 2). I've heard the aircraft fly from unpaved or improperly maintained runways and therefore need this type of modified landing gear if they are going to be landing/taking off from there frequently with such a heavy aircraft.

Compare these two A320's landing gear:


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Viscount724
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RE: Gravel Deflectors & 737NG / Other Newer?

Wed Jan 28, 2009 2:08 am



Quoting JAGflyer (Reply 9):
While we're discussing unpaved runways, Indian Airlines has special A320s with double bogie main gear (4 wheels on each gear instead of 2). I've heard the aircraft fly from unpaved or improperly maintained runways

That double-bogie gear was only on their early A320s. Later deliveries have the standard single-bogie gear. As I recall, the special gear wasn't for use on unpaved runways but on runways with a low bearing strength where the standard gear would risk damaging the surface. I assume the runways in question were upgraded, thus permitting use of the standard gear on their later A320s.
 
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HAWK21M
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RE: Gravel Deflectors & 737NG / Other Newer?

Wed Jan 28, 2009 8:23 am



Quoting Viscount724 (Reply 6):
I expect one reason is the huge temperature variations from summer to winter (e.g. from approximately +25C to -50C) which would make paved runways prone to cracking and a lot of maintenance.

This is educational. Thanks.

Quoting JAGflyer (Reply 9):

While we're discussing unpaved runways, Indian Airlines has special A320s with double bogie main gear (4 wheels on each gear instead of 2). I've heard the aircraft fly from unpaved or improperly maintained runways and therefore need this type of modified landing gear if they are going to be landing/taking off from there frequently with such a heavy aircraft.



Quoting Viscount724 (Reply 10):
I assume the runways in question were upgraded, thus permitting use of the standard gear on their later A320s.

IC or rather now AI has all Twin Main wheels now.also the earlier LG service closed shop,forcing IC to go in for standard equipment as the situation on the runways were vastly improved.

regds
MEL
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Alessandro
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RE: Gravel Deflectors & 737NG / Other Newer?

Sat Jan 31, 2009 2:27 pm

SAAB 340 got a gravelkit as well?
I wonder if a MD-11 could be gravelkitted and land with only the middle engine running or would that practice be too dangerous?
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