Crossunder

Formation flying requires smooth, predictable movement to maintain safe spacing between aircraft. Understanding the crossunder maneuver helps pilots recognize how to transition from one side of the lead aircraft to the other while preserving visual references and controlled closure rates.

Crossunder

Introduction to Crossunder

  • The purpose of a cross-under is to move the Wing from the parade position on one side of lead to the other
  • Cross unders may be used to:
    • Minimize Wing's exposure to sun
    • Area management
    • Breakup and rendezvous
    • Returning to the airfield (overhead maneuver)
  • The maneuver is performed slowly to control movement, and should be not be performed faster than a walking pace
  • There are two methods to perform this maneuver, the box, and the V

  • WARNING:
    All procedures are GENERALIZED.
    Use the Pilot Operating Handbook (POH) procedures for specific aircraft performance and limitations.
    and/or current Standard Operating Procedures (SOPs).
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Crossunder

Cross-under Mechanics

  • Throttles control nose-to-tail
  • Nose controls step-down
  • Angle of bank controls crossing rate
  • All corrections should be "3 part power corrections"
Crossunder

Cross-under Procedure

  1. Cross-under Signal
    Cross-under Signal

  2. WARNING:
    All procedures are GENERALIZED.
    Use the Pilot Operating Handbook (POH) procedures for specific aircraft performance and limitations.
    and/or current Standard Operating Procedures (SOPs).
  3. LEAD: Check the wingman is in position and the area is clear
  4. LEAD: Give the cross-under signal
    • The cross-under signal is a fist held vertically [Figure 1]
  5. WING: Acknowledge receipt of the signal with a head-nod
  6. WING: Simultaneously reduce the power slightly and pitch down to increase step-down

  7. Perform the Step-down:

    • Box Method:

      • Move straight back and down to achieve 10' of nose-to-tail and 15' of vertical separation
      • If the horizontal stabilizer is swept, you will be looking roughly down the leading edge
      • If the horizontal stabilizer is straight, you will be looking at the forward tip of the stabilizer moving toward the trailing edge of the wing
      • Add power to stabilize in position

    • V-Method:

      • Move back at an angle while descending to establish 10' of nose-to-tail and 15' of vertical separation, established in column behind lead
      • Add power to stabilize in position

  8. Perform the Cross-under:

    • Box Method:

      • Simultaneously add power while increasing bank angle to move laterally to the same position, but on the other side of lead
      • Wing must achieve a controlled move to the other side of lead without disturbing the nose-to-tail clearance
        • Wings nose should never be under leads tail, EVER
        • Project yourself outside of leads wingtip to avoid driving too close
      • Add power to stabilize in the stepped-down position
      • Visual cues will remain the same as on the other side of lead

    • V Method:

      • N/A

  9. Return to Parade Position:

    • Box Method:

      • Simultaneously add power and increase pitch to maneuver back into parade position

    • V Method:

      • Complete the other side of the V, simultaneously adding power and increasing pitch to move back into parade position
  10. Cross-under Signal
    Cross-under Signal
Crossunder

Cross-under Common Errors

  • Failure to observer/recognize the cross-under signal given by lead
  • Excessive control inputs
  • Not applying power early enough to prevent excessive drift aft of lead
Crossunder

Crossunder Conclusion

  • Remain mindful that performance calculations are usually more optimistic than actual performance
  • Formation maneuvers are unfamiliar to most in general aviation, requiring in-depth preflight briefing, communication, and practice
    • Do NOT treat these maneuvers haphazardly as the risk of mid-aid collision is clearly greater
    • Maneuvers should always be practiced with an instructor experienced in formation flight before attempting
  • Consider actual versus realized performance when doing any performance calculations
  • Consider practicing maneuvers on a flight simulator to introduce yourself to maneuvers or knock off rust
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Crossunder

Crossunder References