Ground Minimum Control Speed (VMCG) Testing of Transport Aircraft

Abstract

The certification of ground minimum control speed (VMCG) is addressed in the US by 14 CFR Part 25.149 and in Europe by EASA CS 25.149. These requirements call for flight testing to demonstrate the minimum control speed on the ground with the critical engine failed and with rudder control alone. Use of asymmetric braking or nosewheel steering is not allowed in the determination. The path the airplane takes from the point of critical engine failure must not deviate more than 30 feet (9.14m) toward the failed engine from the runway centerline. The test is conducted with the maximum available thrust on the operating engines, and at the most unfavorable weight and CG position. Corrections may be analytically applied for maximum tolerance thrust as well as minimum tolerance rudder deflection. We will discuss the use of the results of this testing in determining operational takeoff speeds (V1 and Vr). Airbus and Boeing conduct VMCG testing using common technical approaches, to harmonized regulations, but with differing methods in the flight test environment. We plan to address areas where our two approaches are common as well as exploring areas where we differ on our technical approach. One specific area of difference involves the termination of the condition. One could choose to reject the takeoff condition (RTO) or continue the takeoff following the recovery from the deviation. Pros and cons of each of these methods will be discussed. The various ways of testing modern jet transports for VMCG certification will be discussed. The maneuver description, test preparation, test conduct, runway suitability, environmental considerations and test analysis will be covered by our team of presenters. As this testing is typically considered to be of high risk, much care must be taken in preparation for the test. The validation techniques employed by both companies in preparation for a flight test campaign will be reviewed. These include flight characteristic predictions as well as pilot-in-the-loop simulation rehearsals. Simulation has become a key preparatory technique for both companies. Safety issues govern much of the preparation for VMCG testing and this will also be reviewed. The potential for unexpected characteristics will be broached. Each company’s safety management issues dealing with this test will be discussed. Finally, the lessons learned accumulated from past VMCG testing will be shared. For example, time critical instrumentation failures resulting in late recover calls, the hidden effects of a light cross wind, and unexpected changes in pilot reaction time. 1 Senior Lead Engineer, Aerodynamics Engineering, P.O. Box 3707 MC 0R-120, and AIAA Associate Fellow. 2 777 Deputy Chief Test Pilot, Boeing Test & Evaluation, P.O. Box 3707 MC 14-HA. 3 Experimental Test Pilot and Safety Advisor, Engineering and Flight Operations, AIRBUS, 1 Rond-Point M. Bellonte 31707 Blagnac Cedex, France. 4 Flight Test Engineer, Engineering and Flight Operations, AIRBUS, 1 Rond-Point M. Bellonte 31707 Blagnac Cedex, France. American Institute of Aeronautics and Astronautics 1