Commercial Certification (FAA)
25.149(e)
Minimum Control Speed
Vmcg
Vmcg
1. Work from high speed to low.
2. Light GW and aft CG worst case.
3. Nose wheel steering disengaged or lift nosewheel off runway to simulate slick runway.
4. No differential braking
5. At least one fuel cut to investigate difference with idle chops.
See AC 25-7A Para 23 b(3)
Aircraft departs runway
Civil Transport (Part 25)
Turbofan
Inhabited Aircraft Only
High
Hazardous consequences of poor test technique; high proficiency in test technique and type aircraft proficiency required.
1. Initiate Abort Procedure
2. Apply directional control
If runway departure is imminent
3. Cut engines
4. Cut all electrical power
When aircraft stops
5. Perform emergency egress
1. Tire failure / gear collapse
2. Thrust asymmetry
3. Primary flight control failure
4. Vmcg greater than prediction
1. Test pilots knowledgeable in the aircraft and experienced in Vmcg testing.
2. Tests previewed in simulator.
3. Conduct work-ups with reduced asymmetric thrust (e.g. perform engine chop to Idle).
4. Testing is conducted during several test runs, with the initial fuel cut occurring at a speed well above the anticipated minimum control speed.
5. If aircraft directional control cannot be regained, retard the operating engine to idle, and abort on the runway. It is not advisable to force the aircraft into the air at low speed, even if departure from the runway is imminent.
6. Engage NWS if required for directional control. Ensure that rudder pedals are close to neutral at engagement to avoid large yaw inputs.
7. All testing shall be conducted under day VMC conditions on a smooth, hard surfaced dry runway. Winds must be 5 kts or less from any direction, except no tailwinds are permitted.
8. Real time monitoring of critical parameters (tire temps, gear loads, engine health, centerline deviation, etc.)
9. Brief abort procedures (throttles up and go; throttle back and stop)
10. Inspect wheels, tires, and brakes at regular intervals during the testing.
11. Minimum Crew to wear helmets and gloves.
12. Flight crew to review emergency evacuation procedures.
13. Select runway of sufficient length and width to perform the testing.
14. All vehicles and personnel must be at least 400 ft away from runway.
15. Ground support personnel to be available with support equipment, cooling fans, etc.
16. Egress doors available & functional.
Emergency Procedures:
a) Turn nosewheel steering ON. Reduce Power Lever Angle (PLA) to IDLE to minimize any asymmetric thrust, use all flight controls, braking and nosewheel steering as required to regain aircraft control.
b) If nose gear is not in contact with the runway during the Vmcg test, apply Nose Down force. Turn nosewheel steering ON. Reduce PLA to idle to minimize any asymmetric thrust, use all flight controls, braking and nosewheel steering as required to regain aircraft control.
Reduces Probability
Analysis
