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Mystery topic. What exactly is Fuel Proportioner? What does it do?

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59 minutes ago, DmitriKozlowsky said:

So its just an automatic fuel transfer system switch. I was hoping for something more exotic that is specific to Pegasus.


It isn't even that. It won't correct an existing imbalance, it just does its best to ensure an imbalance doesn't happen in the first place.

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A fuel sequencer then. To decide which tank(s) the fuel is fed from to maintain CG. I don't see a specific CG gage in the pit, that means that CG travel and position can be deduced from fuel totalizer. In FBW, AFCS compensates automatically for CG shifting forward or aft (depending on a/c type) as internal fuel is burned. In large crew types, the the job of CG management is co-p's. Full time job for B-52 co-p, as aircraft is mostly a flying fuel tank. In Col. Richard Graham's "Flying SR-71" book (1998) , he describes fuel transfer and CG management as one of core tasks of crew requiring constant attention. If CG was allowed to get far aft, the SR-71 flew in nose high attitude incurring drag, burning more fuel, potentially affecting mission performance, and could cause loss of control if not corrected for by trim.


Not really a problem for Harrier, as it is too small, and too short ranged,

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“The tanks are divided into two feed groups, the left feed group consists of the left external tank(s) (when installed), left internal wing tank, left and right front tanks and the left center feed tank. The right feed group consists of the right external tank(s) (when installed), right internal wing tank, rear tank and right center feed tank. Tank pressurisation by regulated engine bleed air, transfers fuel from the tanks of the left and right groups to their respective center feed tank, where fuel pressure to the engine is then increased by a boost pump in each feed tank and a fuel flow proportioner.” This from A1-AV8BB-NFM-000, sec 2-7.


From this it seems that the proportioner is part of the engine feed system, to ensure a commensurate volume of fuel related to throttle position.

It may play a part in balance, for and aft won’t be as serious as port and stbd balance issues.


I will say though, that the Harrier wasn’t my aircraft when I flew, I never fancied doing press-ups from a hide! Lol.

Thats just what it appears to be to me. Happy to bow to exact knowledge of this airframe however (see what I did there?!? Lol!).



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