MaxNr(at)aol.com
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 Posted: Sun Dec 03, 2006 8:53 am Post subject: Fuel systems |
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Do not archive
The following "stream of consciousness" may have a germ of info for those with time to read it. Its sunday. I'm bored. It deals with turbine helicopter systems that I have known: Sikorsky 76 and Bell UH1-212-412-214ST.
Type cetification: Sikorsky certified in FAA NE region. Required seperate tanks to isolate possible fuel contamination in any tank. Bell certified in the SW region. FAA SW didnt care about this.
Tanks/cells: Sikorsky has two 141.5 gal TANKS, one for each motor. Mechanical fuel valves with cross feed. Bells have one filler into a big common fuel cell that that trickle down to series of 4 to 8 (depending on type,variant) cells under cabin floor. Left cells direct to no.1 engine, right for no.2. An elec. operated valve can be used to open an interconnect in bottom cells when level below 400 lbs. Elec operated on-off valves.
Gauges: Sikorsky has one per tank. Capacitance with float type low level warning L/R. Bell has one gauge for the whole mish-mash, capacitance, with float type low level warn. Left and right.
Pumps: Sikorsky uses engine driven pumps to start with JET INDUCERS for each engine to supplement the engine driven. Each jet inducer has a branch to the other eng and can feed both if an eng driven pump fails. Jet ind sort of like a venturi. Bell uses submerged boost pumps in lower cells. Both systems lift fuel about 5 feet to the engine driven pumps. If any Bell looses a boost pump, a 6,000 ft ceiling is imposed. You can guess why. A Sikorsky can fly up to its max allow. alt of 15,000 ft. with only jet ind. Fuel flow for both runs 300 to 450 lbs/hour, more with one eng inop.
Two very different systems as a result of two FAA regions that type certified them. Parts some time break in Bells and poor lower vents slow refueling. Both very dependable. Both are certified in transport catagory FAR part 29.
I've taken too much of your time.
My XL will have single elec pump ahead of the gascolator and 3 position valve.
do not archive
Bob Dingley
XL- rudder- Lyc [quote][b]
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