Document
A Discussion of the Last Flight of X-‐31A
Aircra8#1
Patrick C. Stoliker Dryden Flight Research Center May 2011
As most of you know the flight did not end well
The X-‐31A had flown lots of flights
X-‐31Enhanced Fighter Maneuverability
• The original goal of the X-‐31 AircraB was to demonstrate the feasibility and advantage of post-‐stall maneuverability using thrust vectoring to provide precise control up to 70° angle-‐of-‐ aGack • Requirement was for unlimited maneuverability
Envelope Expansion
• AircraB began operaLons from Palmdale, conducLng iniLal envelope expansion up to 30° AOA – 110 flights conducted between the two aircraB • The flight envelope was expanded to 70° AOA aBer moving to Dryden – Started with 1g entries – Proceeded to elevated g entries, followed by abrupt sLck inputs – Approximately 171 flights
Flight Research Flights
• AircraB performed approximately 210 flights related to close-‐ in-‐combat – Basic Fighter Maneuvers – One versus one with NASA F-‐18, Navy F-‐14, Air Force F-‐15 and F-‐16 aircraB – Helmet mounted display evaluaLon – Standard EvaluaLon Maneuvers for high angle-‐of-‐aGack handling qualiLes • Approximately 40 Quasi-‐tailless experiment flights • A number of fluGer-‐test-‐box/parameter idenLficaLons flights • 522 flights had been completed by January 19, 1995
January 19 was an ordinary flying day
Dryden Airworthiness and Flight Safety Review
Process
Airworthiness and Flight Safety Review Reports, Flight Readiness Tech Crew Review Transfer Brief Preliminary Concept Post Critical Design Definition Tech Flight Design Brief Review Review Debrief Review Fabrication, Integration Formulation Flight/Test Operations Design and Testing Project Project Life Cycle !
Day-to Day Airworthiness Approval & Flight Safety Review Activities
FRR/AFSRB Flexibility
Project and Center Chief Eng. review plans and preparations Complexity, Criticality, Low High Risk Scale Chief Eng. Review Chief Eng. Review with AFSRB Review Review Indep. Flight small group of experts Level Readiness Rvw.
Approved to fly with crew brief FLY Approved to fly with tech brief Approved to fly with operational readiness review
Airworthiness and Flight Safety Review Process
Director considers AFSRB recommendations; either approves Dryden !
platform for flight or directs project team to Center Director !
provide additional risk mitigation " AFSRB formulates a recommendation letter to the Center Director documenting flight safety risks " Airworthiness and !
Standing board of Dryden senior managers chaired by Flight Safety !
the Dryden Chief Engineer " FRR prepares written report of Review Board !
findings/recommendations and Project provides briefing to AFSRB " response to FRR findings for AFSRB " Flight Readiness !
Project Team !
Review Committee !
Comprehensive review of Responsible for design, Totally independent team of technical analyses, development, integration, disciplinary specialists chartered to operational procedures, verification and validation, hazard assess project ʼ s overall readiness documentation, hazard/risk analyses, risk management, flight for flight, categorization of hazards, management, qualification test qualification, flight test, flight probability of mission success, and results, and flight/ground/ operations " flight/ground/range safety range safety " procedures "
What gets covered in a Tech Brief?
• Review of past flight conduct and • Mandatory Mission Requirements results – Go/No Go List – Mission Rules • ObjecLves of proposed flight or – Weather Constraints flight block – OperaLng LimitaLon • Flight Plan – Emergency Procedures • AircraB Status • Dryden range, facility and – Maintenance Status informaLon technology – InstrumentaLon Status requirements • ConfiguraLon – ConfiguraLon Changes – Open Waivers • Control Room OperaLons • Hazard Review – List all Hazards – Hazard AcLon Matrix
There are no perfect processes
Preparing for the Final block of Flights
• The aircraB was in a block of rouLne flights – High angle-‐of-‐aGack flying qualiLes flights had just been completed – A Tech Brief was held prior to Dec 6, 1994 presenLng a flight block for a series of Quasi-‐tailless and parameter idenLficaLon flights – A mini-‐Tech brief was held Dec 14, 1994 for a minor soBware revision – A crew brief was held January 18
Crew Brief Contents
• Mission Specific Items – Pilot assignments – Review of Flight Cards – AircraB Frequencies – Weather th • January 18 we briefed three flights – Two Quasi-‐tailless ground aGack using the ATLAS light system – One parameter IdenLficaLon Flight • Up to 40° AOA, 20kB – We discussed the weather and the need to stay out of visible moisture and stay below the clouds
Weather CondiLons for the day of Flight
Lesson Learned on Mission Rules
• The X-‐31A had a Mission rule precluding flight in visible moisture.
• The X-‐31A SHOULD have had a mission rule precluding flight in visible moisture or icing condiLons • I know of one program that had a mission rule precluding flight below 5000 B AGL – How are you going to land?
• Make sure the mission rules concise and make sense.
th
January 19 Mission Day
• Flight 1-‐290 took off at 9:40am, landed at 10:22am • Flight 1-‐291 took off at 11:42am, landed at 12:29pm • Flight 1-‐292 took off at 1:46pm – One parameter idenLficaLon maneuver at 40°AOA, the remainder of the maneuvers were at 10-‐20° AOA – During the flight, engineers and pilots noted inconsistencies between airspeed and angle of aGack • They were not adequately discussed on the intercom – The pilot reported turning on pitot heat • Message that there was no pitot heat did not get transmiGed to the pilot promptly – Could not complete the last Parameter ID input – AircraB departed controlled flight during Return to Base checklist
Speak up when something is not right!
Lesson Learned on Vigilance
• You can’t treat every flight like a first flight, but you can treat every flight as an important flight.
• Retain control room discipline – In terms of monitoring systems unLl the airplane has landed – IdenLfying anomalies – Proper Control room communicaLons on the network – And relaying informaLon to the pilot • Proper cockpit markings – Pitot heat should have been marked inoperaLve – Kiel probe had been on the airplane for 300 flights!
Flight Test is about being Prepared
Be Aware
INU Velocity Air Data Velocity Data ploGed on January 24, 1995. Airspeed measurements between the InerLal NavigaLon System and Air Data began diverging 20 minutes before the mishap!!