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Old 15th Jul 2010, 14:02   #1 (permalink)
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Aerial Spraying From B737

Have any of you techies been involved in the flying or conversion of B737 (probably the QC model) in an airborne spraying fit? I gather there is a STC out there somewhere and would very much like to get my hands on the details?
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Old 15th Jul 2010, 15:37   #2 (permalink)
 
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There was a program started in Canada to fit a 737-200 with a belly mounted retardent tank for aerial forest fire suppression but I would be very surprised if a spray rig would work. Spray systems consist of a series of nozzles below and behind the wing. The flow rate is fairly low and a lot of work is put into palcing the nozzles so that they exhuast into smooth air. The underwing mounted engines of a 737 would put so much heat and turbulance into the pattern I would guess you could only put nozzles at mid span and outboard which would put a big gap into the middle of the pattern. Also I cannot think how you would mount the nozzles and still allow full flap operation.
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Old 15th Jul 2010, 16:30   #3 (permalink)
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ExCreamie

I was thinking of mounting the spray arms well aft as per C130/L100 style with the dispersant chemicals carried internally - so you have to penetrate the pressurised hull as part of the STC. Problem is that the Hercy bird is naturally the weapon of choice but finding airframes with the necessary life expectancy is testing to say the least. A good 737 costs 10% of a good C130. Not that I much fancy the idea of 140kts at 100' amongst the seagulls with 2 jet engines!
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Old 15th Jul 2010, 21:56   #4 (permalink)
 
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Plenty of information here.
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Old 15th Jul 2010, 22:11   #5 (permalink)
 
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Old 19th Jul 2010, 10:25   #6 (permalink)


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Spray adaptations

I don't think the actual spray modification would be difficult although as a correspendent says it would require cutting into the pressure hull - need to get some good clas though! The interesting bit is the in-aircraft dispersant aspects (tankage needs to be vented externally thus pressure vessel, fluid has SG approx 1 so high denstity: both Cof G locations and floor strength need to be considered.
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Old 29th Jul 2010, 11:05   #7 (permalink)
 
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Who cares how hard it is to acheive what a job im in if you need a driver!!!!
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Old 29th Jul 2010, 11:14   #8 (permalink)

 
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What am I missing here? I keep seeing mention of 'pressure vessel'. As pressurisation only applies to ferry/positioning flights why is it an issue? There must be dozens of temporary ways to take pipework from inside to outside.
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Old 29th Jul 2010, 17:13   #9 (permalink)
 
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Old 30th Jul 2010, 11:35   #10 (permalink)
 
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Assuming this is not a windup, and assuming it is about spraying Gulf-sized areas rather than poppy fields, I fear that you are way off track in envisaging Pawnee-style kit - 'spray arms' - being strapped to a 737. Furthermore, the prospect of flying a 737 at crop-spraying height over an oil-smoothed surface is not one which would appeal to me - or to cirr737's insurers! - it is inappropriate, and unnecessary.

The essential challenge (apart from keeping the CofG about right) is in securing a spray discharge with the right droplet size range. (Bear in mind that droplet formation is governed by the free surface energy characteristic of the liquid, and that that of a dispersant may differ from those of agri-fluids).

Overcome that, and Stokes' Law is your friend. You may achieve good and wide surface distribution from a sensible and safe height without spray arms, and indeed without any new penetrations of the pressure hull. ( If you are serious and need more 'gen feel free to PM me ).
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