RansMail #015 April 19th 2004

a)    I'd like to welcome owner Geoff Scott, who wishes to join in with us. We have had a chat by 'phone he is still learning and converting to 3 axis & confirms he is the chap with the yellow S4  at Chatteris.  

b)    I have so far only quickly weighed the S4 in the hangar on 'calibrated' bathroom scales, allowing for an estimated 16 lb. of fuel still in the tank(but forgot the cockpit was holding its funnel, hose and oil bottles) the near empty weight totals some 341 lb. Therefore a more exact and officially witnessed weighing is called for, because this predicates a whopping 38 lb. lighter than the recent 2003 'official' weighing. 

Now I don't want to upset the Inspector or rock the PFA boat, so will have to use this raw information with care. However it would allow the top tank (it weighed 6 lb. dry) to be refitted & full of fuel still leave the total with me as P1, safely approx. 7 lb. under the 587 lb. max allowed AUW.

c)    In view of importance of b), I decided to recheck the fuel tanks' capacities, etc. ?

The original handwritten submission for my a/c, -FW (1991), to the PFA states 20 litres: & the weight & balance figures 'allowed' for fuel at 30 lb. 
The Rans' yellow sales sheet from the same era, I have here, is silent.
The current web specification off Sportair gives only "9 U.S. gallons" = 7.52 Imperial gallons = 34.15 litres; which I therefore assume must be the biggest two tank version.
A modern web article, I found, appraising the S4 by an Italian owner state it's 18 litres.
Graham has already told us the top is nominally 16 (12 or) litres: therefore 34-16=18 litres ?  (alternatively 34-12=22) 

My top tank actually has the 'sharp' rear end; Graham says it indicates the 12 litre version. Confirmed by cubic measurement ~1/2 cubic ft volume, which allowing space for the top vent, is close to 3 U.S. gals~12 litres. Thanks, Graham, that made it a lot easier having your info. to hand.

d)  In the interest of accuracy I also looked up the specific gravity of mogas & found it ranges between 0.71 & 0.79, which averages  0.75; whilst my 1955 Collins Engineers diary says 7 1/2 lb. per gal. = 0.75 kg per litre, = 1.65 lb./litre ..............A curious mixture of metric and Imperial measures !!  
But at least 18 litres X 1.65 lb.'s = 29 3/4 lb, so I accept the fus. tank capacity as 18 litres. The top tank when installed and filled will add a modest 6 lb.+(12 X 1.65) = 26lb.

e)   Like Don, I'm still trying to find a neat fuel management solution. I would also need to find the supplier of nice tap, say,  "Left/Off/Right";  but this doesn't cover the drain down phase for getting the balance from the top tank completely into fus. tank. Otherwise one simple "On/Off" tap for the top tank only, could do the whole job, provided I don't get confused. Thinking the latter system through, this should work thus:- 
Take off and initial flight, fus.tank only: when its down to ~5 litres, turn on top tank too. 
and that's it; & before refuelling close top tank tap. 

What's the group think ?

Mike Hallam.