FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1951
1951 - 2536.PDF
21 December 1951 779 FUEL MEASUREMENT Precision Surveillance of Consumption : An Ingenious New Meter FOR the pilot of any modern aircraft, be it the Brabazonor a fighter, the precise knowledge of the amount offuel in the machine's tanks at any instant is vital—not so much in itself, perhaps, but acutely in relation to the flight time expended and anticipated, the flight conditions existing and expected, the engine settings, weight distribution and, in short, all the circumstances which permutations of these and their related factors can combine to produce. George Kent, Ltd., of Luton, Beds, have tackled the problem by devising automatic fuel-flow meters in the form of a transmitter which, interposed in the fuel line, measures the fuel flow rate and accordingly sends electrical impulses j to a receiver which counts the signals and displays the information—in any standard unit of measure required— on the pilot's or flight engineer's instrument panel. The transmitter unit comprises a light-alloy cast body in the upper part of which is housed the contact head, this being physically isolated by a joint-plate dividing off the lower compartment which accommodates the gear train and working chamber and embodies the inlet and outlet orifices. Depending on the type of transmitter, the shape and size varies, and the internal drive between gear train and contact head is conducted either by vertical shaft through a packed gland, or by means of a magnetic coupling. Available in three versions, medium capacity/low pressure, high capacity/high pressure, and high capacity/low pressure, the respective designations of the transmitters are MA.4504, MA.4506 and MAL.4002. The first-mentioned type has a working capacity of 11 to 400 gal/hr (100-2,880 lb/hr) with a maximum pressure-loss of 3 lb/sq in at maximum flow, the normal working pressure being 30 lb/sq in. For the MA.4506 unit the working capacity is up to 1,250 gal (up to 10,000 lb) per hour, with a pressure-loss of 12 lb/sq in at maximum flow; the maximum working pressure is 1,100 lb/sq in. Similarly, the MAL.4002 has a working capacity of 60 to 1,000 gal (480-8,000 lb) per hour, a pressure loss of 3 lb/sq in at maximum flow, and a maximum working pressure of 30 lb/sq in. Fuel enters from beneath the working chamber and, in passing through it, drives the rotating assembly, to emerge through a port in the top of the chamber and so flow to the outlet orifice. The working chamber is, effectively, a brass drum in the lower part of which is a hub embodying an annular race for a roller. The roller is carried by the diaphragm of what is called the piston, albeit its motion is semi-rotary rather than reciprocating. This piston is, in fact, rather like a cylinder divided at mid-height by a diaphragm (the axis being that of the roller) and radially slotted for a tongue running from the chamber wall to the hub. The motion of the piston resulting from fuel flow through the chamber is shown in the diagrams. Coaxially with the roller, but above the piston diaphragm, is a pin which engages an arm off the end of the vertical drive shaft, rotation thus being given through gear trains and/or magnetic couplings to the switchgear of the contact head. This comprises a gear and cam mechanism together with a switch—in essence, a make-and-break system to transmit impulses to the receiver units. Just as there are different capacity transmitters, according to duty, so are there different receivers, although all types of receiver can operate with all types of transmitter. George Kent, Ltd., themselves make a receiver presenting the information in terms of gallons gone, whilst Smiths Aircraft Instruments, Ltd., make exclusively for Kents two types of receiver, one indicating rate of fuel flow and the other giving the same information plus the totalizing of gallons gone. Kent's gallons-gone receiver can alternatively be calibrated to indicate pound (weight) of fuel used and, of course, all receivers can be supplied calibrated in Imperial, U.S. or metric units. The indicator mechanism is housed in a large S.A.E. case modified and extended to house the driving motor and Diagram No. 1 shows the inlet port open to the interior of the piston (solid lines). In-flowing fuel causes the piston to start a semi-rotary movement, sliding along the division tongue and displacing the neutral fuel (dark stipple) which, in turn, becomes exhaust fuel (broken lines) as shown in Diagram No. 2. At No. 3 is shown incoming fuel on the inlet side of the chamber with neutral fuel inside the piston and cut off from both ports, and at No. 4 is the end of the exhaust stroke, with the piston about to open the inlet port. • electric components. A cylindrical can is fitted over the rear portion to screen the assembly, electrical connections being made through a three-pin Breeze plug. In the rate and totalizing indicator the rate portion of the instrument is a chronometric mechanism which operates by counting the number of impulses received from the contacting mechanism of the flow meter during a given time interval. The time interval is part of a time cycle governed by a clock- type balance wheel and escapement, which last is maintained by a 24-volt D.C. motor that runs continuously and drives the escapement through a spring drum and friction drive. The driving torque applied to the escapement is governed by the torque exerted by the friction drive, while the spring drum (which, during regular operation, remains wound) serves only to store sufficient energy to maintain the operation of the escapement for at least two cycles after being switched off, so enabling the pointer of the indicator to return to zero. Dec. Jan. Jan. Jan. 21. 11. 18. 18. Jan. 19. Jan. 19-20. Jan- 28 Feb. 1. Jan. 29. Feb. Feb. Feb. Feb. 11. 15. 20. 22. Feb. 23. FORTHCOMING EVENTS Institute of Navigation: "Meteorology and Navigation," by Lt. Cdr. P. G. Satow, D.S.C., R.N. A. and A.E.E., Boscombe Down: Contractors' Dinner. Helicopter Association: "A Review of Helicopter Patents," by L. H. Hayward. Institute of Navigation: "Navigational Errors," by W/C. E. W. Anderson, O.B.E., D.F.C., A.F.C. Aircraft Recognition Society: Hurricane Trophy Competition. Vintage Aeroplane Club : Rally. Institute of the Aeronautical Sciences: 20th Annual Meeting, New York. Society of Instrument Technology: "Mechanical Consideration in the Design of Servo Systems," by Prof. A. Tustin. Institute of Transport: Brancker Memorial Lecture, by Capt. E. D. Clarke, M.C. Institute of Navigation: "Navigation Aids for Military Air- craft," by S/L. D. Bower. British Institution of Radio Engineers : "Search Radar for Aircraft," by P. L. Stride. Helicopter Association: "Helicopter Power Plants," by A. Graham Forsytb, B.Sc, F.R.Ae.S. Society of Licensed Aircraft Engineers: Main Lecture: "Some of the Responsibilities and Problems of an Airworthiness Authority," by R. E. Hardingham, O.B.E., F.R.Ae.S., M.S.LA.E.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
