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TRIP warning in HUD?


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Hi guys,


Last night when I flew the Viper I got a message/warning on the HUD, bottom left, below NAV (I think) that said something like TRIP . I looked through all sorts of F16 manuals but couldn't find what it means.


I did get a BINGO warning prior to that and I did refuel air-to-air once. I can not remember exactly when the warning came but it would have been after the BINGO warning.



Does anybody know what this warning means?

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  • 1 year later...

Hi, a bit late but here's the deal:

A trapped external fuel condition is indicated by flashing TRP FUEL and FUEL in the HUD.

Five conditions must be met for a TRP FUEL warning to occur.
Conditions are:

  • FUEL QTY SEL knob is in NORM.
  • Aerial refueling has not occurred within previous 30-90 seconds.
  • Fuselage fuel has been at least 500 pounds less than fuselage capacity for 30 seconds.
  • Total fuel has been at least 500 pounds greater than fuselage fuel for 30 seconds.
  • Fuel flow has been less than 18,000 pph for 30 seconds

Certain malfunctions can cause fuel to be trapped in the external tank(s).

The tank(s) in which fuel is trapped can be detected by a periodic check of external tank fuel quantities.
Accomplish steps 1 through 8 and 9 (if required) without delay:

  1. Fuel flow - Minimize.
  2. AIR REFUEL switch - Confirm in CLOSE.
  3. AIR SOURCE  knob - Confirm in NORM or DUMP.
  4. TEMP knob - MAN and adjust for comfort. This action usually increases ECS air pressure for external fuel transfer.
  5. TANK INERTING switch - TANK INERTING to reduce internal tank pressurization.

    Selecting WING FIRST bypasses electrical components that, if malfunctioning, can prevent fuel transfer from external wing tanks, the centerline tank, or all three external tanks. With a three tank configuration, the first indication that the centerline tank is feeding is after the external wing tanks are emptied.
  7. ENG FEED knob - NORM.
    A NVP TFR FAIL PFL and a fly-up can occur when NORM is reselected while operating in TFR.
  8. Stick - Pulse aircraft in pitch several times by applying differential g forces of approximately -+2g.
    If the AIR REFUEL switch was initially found in CLOSE (step 2), perform step 9. If the AIR REFUEL switch was  initially found in OPEN (step  2), omit step 9.
  9. AIR REFUEL switch - OPEN (1 second), then CLOSE.
    Open  or close AR door at or below 400 knots/0.85 mach.
  10. External tank fuel quantity - Monitor.
    The time required to observe fuel transfer if the malfunction is corrected can vary from 13 minutes (for a full centerline tank) to 1012 minutes (for three external tanks with 500 pounds fuel in each) if reservoir tanks are full (i.e., both air ejectors are off).

    If a trapped external fuel condition is not discovered until either reservoir tank is less than full or a fuel low light is on, sufficient fuel transfer from the external tank(s) may not occur even if the malfunction is corrected. Consider fuselage fuel to be the only usable fuel.

    If trapped external fuel occurs after air refueling and completion of checklist steps did not correct the malfunction, consider descending well below the freezing level to unfreeze the external pressurization and vent valve. Cycling the AR door at lower altitude may restore normal operation.

  11. Stores-Jettison (if required).

Ref.: Flight Manual T.O. GR1F-16CJ-1

I recently had one occur on my aircraft after aerial refueling but didn't know the procedure.


Edited by SgtNickElis
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