Why does the Typhoon vent fuel in displays
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The vent system is probably working as intended. Its main function is to prevent high differential pressures across the fuel tank wall; fairly key for CFC structure. These can arise from either high climb and dive rates or from high delivery rates from the tanks. Any fuel migrating into the fill and vent lines will be lost overboard as the valves open. The 2:34 one is probably due to the steep climb; 1:57 just might be fuel slosh from the vigorous manoeuvres.
The interesting bit of the photo is the vortices shedding from the 'moustache' strakes on the avionic bay doors. They work to help the fin and directional stability at high incidence.
EAP
The interesting bit of the photo is the vortices shedding from the 'moustache' strakes on the avionic bay doors. They work to help the fin and directional stability at high incidence.
EAP
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AI R, i'm not privvy to any detailed info re the flying kit Typhoon pilots wear (being a civvy) but, i do seem to remember watching an interview with Craig Penrice(?)
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Originally Posted by thing
That name rings a bell, ex Lightnings?
I think he used to post on here as 'Tarnished'?
-RP
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Nasty indeed. Remembered why I know his name, behind me as I type is a framed picture of a Lightning with all of the last guys signatures on it, including his! Doh...
I'll bite and try to add to the various explanations.
First the humorous one: It' s a wet system machine and as long as it is venting fuel there' s everything ok, enough of it still available.
Now to the logic explanation. The tanks are pressurized, to prevent the collapsing of the rubber type self sealing fuselage tank cells during high g maneuvering (at least that was the case in aircraft like F4 and other pre typhoon jets).
In normal operation the tanks are kept full by the transfer pumps (external and internal transfer), and when no transfer fuel is available those tank cells will go empty and stay empty, therefore there will be no repeated filling and emptying of single tank cells. They are either full or while getting emty they are pressurized with bleed air and stay pressurized until landing.
During display asociated with high powersettings the fuel volume of some cells will decrease, as the internal or external transfer pumps are not able to refill the tanks in the same time as fuel is used by the burners. The depleting fuel volume is replaced by pressurized bleed air. When the tank cells fill up again the bleed air is vented overboard, thus taking some fuel with it into the vent lines, especially just prior full fuel state of the respective cell is reached again.
Hope that helps.
First the humorous one: It' s a wet system machine and as long as it is venting fuel there' s everything ok, enough of it still available.
Now to the logic explanation. The tanks are pressurized, to prevent the collapsing of the rubber type self sealing fuselage tank cells during high g maneuvering (at least that was the case in aircraft like F4 and other pre typhoon jets).
In normal operation the tanks are kept full by the transfer pumps (external and internal transfer), and when no transfer fuel is available those tank cells will go empty and stay empty, therefore there will be no repeated filling and emptying of single tank cells. They are either full or while getting emty they are pressurized with bleed air and stay pressurized until landing.
During display asociated with high powersettings the fuel volume of some cells will decrease, as the internal or external transfer pumps are not able to refill the tanks in the same time as fuel is used by the burners. The depleting fuel volume is replaced by pressurized bleed air. When the tank cells fill up again the bleed air is vented overboard, thus taking some fuel with it into the vent lines, especially just prior full fuel state of the respective cell is reached again.
Hope that helps.
Last edited by RetiredF4; 29th Aug 2013 at 16:28.
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RetiredF4, thanks for the explanation, makes logical sense. I hadn't thought about the rubber tanks collapsing and I can see the fuel venting as the air is expelled.
Now will I be able to remember all of that at next years airshow.
Now will I be able to remember all of that at next years airshow.
