F-16 Operation Flight Trainer (OFT) Flight Model Update
In 1990, the Block 30 OFT simulators were judged to exhibit very benign, non-oscillatory, and unrealistic deep stall characteristics, resulting in little training value for pilots in this dangerous part of the flight envelope. Therefore, Air Force Systems Command (AFSC) requested the
Training Systems SPO (YWFE) to develop a better training simulation for the Block 30 and Block 40 aircraft. YWFE contracted with the simulation manufacturer at the time, CAE Link of Binghamton, NY, to update the flight model under a compressed time schedule due to the identified urgency
of improving the training capability. Following the contractor's initial unsuccessful attempts at improving the deep stall modeling, Bihrle Applied Research was contacted to assist in the flight model update.
Five success criteria were identified for the improved deep stall modeling:
1) Erect and inverted deep stalls entries should reflect the airplane's ease of entry, and should reflect the airplane's percentage of self-recoveries. The existing simulation was unrepresentative in both respects, being too difficult to enter into a deep stall and likely to self
recover.
2) The deep stall should reflect the oscillatory behavior that can occur in the deep stall condition. The existing simulation only exhibited a very benign non-oscillatory deep stall when a deep stall was captured, which ultimately was easy to recover from. Depending on the
configuration and entry conditions, the F-16 can exhibit this type of behavior, but the deep stall conditions can vary from smooth to highly oscillatory. The oscillatory deep stall is more difficult to recover from and was judged a better training condition.
3) The majority of inverted deep stalls should exhibit significant yaw rates (20-30°/sec) with the pilot's feet on the floor, and should be unrecoverable unless the pilot applies the rudder in the correct direction.
4) Manual Pitch Override (MPO) recoveries that are not aggressively tracked to the vertical should transition to the inverted pitch trim condition. This behavior requires the pilot anticipate application of aft stick following upright deep stall recoveries or the airplane can pitch
down with sufficient rate to pitch into the inverted deep stall. The simulation needed to exhibit this behavior as well.
5) The deep stall entries should reflect the behavior of the airplane concerning the c.g., entry attitude, rates, etc. In other words, more forward c.g conditions should be more entry resistant, and easier to recover from. Depending on the entry conditions, the airplane should self
recover, capture an oscillatory or smooth condition, etc.
The basic request was to better physically model the post stall behavior of the F-16. Under the very tight schedule requirements of AFSC, the model was basically restructured above the alpha limiter (approximately 26° AOA) to eliminate the significant amount of model "adjustments"
and accept a more comprehensive aerodynamic database that entailed a significantly more detailed level of model functionality. Bihrle's extensive experience in static and dynamic data acquisition and analysis for this configuration enabled the rapid development of this more
comprehensive wind tunnel data based model. Following the mechanization of the data into the existing OFT format, Bihrle company engineers supported the review of both General Dynamics and Air Force test pilots, successfully meeting the success criteria in less than two weeks of pilot
evaluation.
The success of the model update was demonstrated by the Air Force chief F-16 test pilot, Lt. Col. John Severski, at Luke AFB where he used the simulation application to provide a demonstrable improvement in student pilot recognition and recovery capability. Because of the
enthusiastic acceptance of the training community, the model update was propagated to all versions of F-16 OFTs.
Other Simulation Development and Support Success Stories
Italian
AV-8B II+ Mission Simulator Aerodynamics Model Development
F-15
Keep Eagle Program
F/A-18C/D
Powered Approach Model Development
Ranger
Model Development
The
Wright Flyer Model B Simulator
Grumman
EA-6B Engineering Simulation
Ice Contamination Effects Flight Training Device (ICEFTD) for NASA Glenn Research Center
General
Aviation Configuration Simulation Development Support
