Aircraft with tip tanks question.
#12
In a land of unicorns
Joined APC: Apr 2014
Position: Whale FO
Posts: 6,465
#13
Gets Weekends Off
Joined APC: Jun 2008
Posts: 273
Fueling a LRJET is easy but there is a process. As mentioned there is only one filler point on each side, on the tip.
If fueling using a single point you have to be cautious of an imbalance because it can cause the aircraft to tip. First side fill to a 125gal imbalance. Proceed to the other side and fill to 250gal and then back to the other side for a top off. During the event you’re likely filling the trunk (1200# in a 35) and being mindful of a bubble. If your aircraft is prone to developing a bubble then you can open the cross flow and try to force it out by sending fuel from the full wing into the the with with the bubble. Leave the cap off the bubble side for best results.
You can also taxi or tug the plane in a few circles and it will clear the bubble.
In flight the tips burn down first. After the tips burn down passed 5-600# remaining you can start bringing fuel forward out of the truck. The purpose of this is to verify the function of the jetpumps which use motive flow to move fuel.
Baffles, flapper valves and a yaw damper are used to combat Dutch roll.
If fueling using a single point you have to be cautious of an imbalance because it can cause the aircraft to tip. First side fill to a 125gal imbalance. Proceed to the other side and fill to 250gal and then back to the other side for a top off. During the event you’re likely filling the trunk (1200# in a 35) and being mindful of a bubble. If your aircraft is prone to developing a bubble then you can open the cross flow and try to force it out by sending fuel from the full wing into the the with with the bubble. Leave the cap off the bubble side for best results.
You can also taxi or tug the plane in a few circles and it will clear the bubble.
In flight the tips burn down first. After the tips burn down passed 5-600# remaining you can start bringing fuel forward out of the truck. The purpose of this is to verify the function of the jetpumps which use motive flow to move fuel.
Baffles, flapper valves and a yaw damper are used to combat Dutch roll.
#14
Banned
Joined APC: Feb 2007
Posts: 461
I'm doing some research on fuel balancing procedures for various aircraft. I have no experience with aircraft equipped with tip-tanks and was wondering what the fuel burn procedure is for them? Say a Learjet. I know you have to add fuel to the tanks in a certain order...but what about when you burn the fuel?
Anyone?
Anyone?
The Lear 25 and 35/36 fuel directly into the tip tanks and use pumps to transfer to the center tank. If you're fueling the "tips only: you can fuel full blast with no kick back. If they need to transfer to the center tank, you have to wait longer to re top the tip tanks. The 36 has a bigger center tank so you may have to wait around longer.
The Westwind I has tip tanks but fuels through fuel inlets on top of the fuselage and flows into the wings and tip tanks. There are also manual valves (little sticks under the wing you pull to manually open) to allow fuel to flow to the tips.
The Westwind II had singlepoint.
MU-2 are just monsters. Tip tanks and inner wing tanks. No fuel imbalance over 50 gallons and getting to the 15 gallon inner tanks was always a PITA due to the limited space between the fuselage and the engine. The even had weird fuel caps.
It was always fun to watch the wing drip as you fueled one side or the other. Especially if you were alone. Also, NEVER place a ladder under the wind or tip tank.
Twin Cessnas were interesting, the tips were the main tanks and the wing tanks were the aux tanks (except the later models with out tip tanks like the 414A and 421C).
The return fuel line from the engine flowed ONLY into the main tank (tips) this means you had to burn from the tips for at LEAST an hour before using aux tanks. If you use the aux first, the return fuel will overflow the main tanks the dump the excess overboard.
Also, some of them had nacelle tanks to add to the complications.
I'm pretty sure that bonanza tip tanks were directly piped to the wing tanks, (not 100% sure on this one)
G-2's also had tip tanks but I'm not sure about the fueling requirements and burn on that one.
#16
Holy cow yes! Back in my rampie days we had a corporate outfit with a fleet of 4 MU2's. When they called to ask for fuel, the poor line guy who had to make the trip to their hangar would be gone half the day to fill up those four airplanes. Partially fill one tip tank, then partially fill the other, and back and forth a few times to keep them within balance. Then back and forth between the two wing tanks, and then finally wrap yourself around a couple of the prop blades to reach me main center tank. I HATE(!!!!!) that airplane.
#17
Gets Weekends Off
Joined APC: Sep 2015
Posts: 304
Airplanes with tip tanks vary greatly.
Twin Cessnas were interesting, the tips were the main tanks and the wing tanks were the aux tanks (except the later models with out tip tanks like the 414A and 421C).
The return fuel line from the engine flowed ONLY into the main tank (tips) this means you had to burn from the tips for at LEAST an hour before using aux tanks. If you use the aux first, the return fuel will overflow the main tanks the dump the excess overboard.
Also, some of them had nacelle tanks to add to the complications.
I'm pretty sure that bonanza tip tanks were directly piped to the wing tanks, (not 100% sure on this one)
Twin Cessnas were interesting, the tips were the main tanks and the wing tanks were the aux tanks (except the later models with out tip tanks like the 414A and 421C).
The return fuel line from the engine flowed ONLY into the main tank (tips) this means you had to burn from the tips for at LEAST an hour before using aux tanks. If you use the aux first, the return fuel will overflow the main tanks the dump the excess overboard.
Also, some of them had nacelle tanks to add to the complications.
I'm pretty sure that bonanza tip tanks were directly piped to the wing tanks, (not 100% sure on this one)
There are different manufacturers of Bonanza Tip tanks. You may be right that others transfer to the main tanks. That's the way the locker and nacelle tanks worked in our twin Cessnas.
#18
Gets Weekends Off
Joined APC: Sep 2015
Posts: 304
Holy cow yes! Back in my rampie days we had a corporate outfit with a fleet of 4 MU2's. When they called to ask for fuel, the poor line guy who had to make the trip to their hangar would be gone half the day to fill up those four airplanes. Partially fill one tip tank, then partially fill the other, and back and forth a few times to keep them within balance. Then back and forth between the two wing tanks, and then finally wrap yourself around a couple of the prop blades to reach me main center tank. I HATE(!!!!!) that airplane.
If you'd sent 2 trucks and 2 rampers over, and fueled both sides at once, you could have fueled the fleet in a quarter of the time. Sometimes the whole is greater than the sum of it's parts.
#19
Throw in wing locker tanks and get close to seven hours endurance... which was good because reading and comprehending the fuel management checklist took almost that long. Seven hours without a relief tube was miserable.
#20
Line Holder
Joined APC: Jul 2018
Posts: 28
Not sure how it works in a Learjet but the 172 I fly has tip tanks. They do not feed the engine, instead, they just dump into the mains when I turn the pump on. The main must be at least half empty before I can pump, then I have to switch to the other tank because the tank being filled cannot be feeding the engine. I just flip the switch and it fills, takes about 10 minutes to empty the tip tank, 11gal usable each side.
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