Fgt altitude deviation excursion from clearance altitude.

Attributes
ACN	145069
Time
Date	199005
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : nfl
State Reference	NY
Altitude	msl bound lower : 30000 msl bound upper : 32000
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Controlling Facilities	military facility : nfl
Operator	other
Make Model Name	Fighter
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	government : military
Function	oversight : pic
Qualification	pilot : military
Experience	flight time last 90 days : 150 flight time total : 3600 flight time type : 1450
ASRS Report	145069
Person 2
Affiliation	government : military
Function	oversight : pic
Qualification	pilot : military
Events
Anomaly	airspace violation : exit altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During check in with agency responsible for special airspace control, our flight was cleared onto range and given altitude cap of 30000' MSL. This altitude was stated as, '3-0-0,' but was understood as '3-3-0.' while setting up for a supersonic intercept we climbed to FL300 and accelerated to approximately 1.3 mach. As the aircraft passed approximately mach .98, the pitot/static INS began to fluctuate +/- 2000' due to the shockwave moving over the static ports on the aircraft. This continued as the aircraft accelerated through mach 1 with the altimeter stabilizing near 32000'. As we believed our airspace extended to 33000', we completed the intercept at this altitude. After the run our wingman called to say that range control had been calling on guard frequency (243.0) to advise us of our altitude excursion. However, we were not monitoring guard due to an ELT beacon on that frequency. Upon deceleration below mack 1 altimeter showed 29500'. Supersonic cruise is a known problem in the aircraft with respect to pitot static errors. A large altitude buffer is required when conducting supersonic flight operations. Contributing to the confusion was a false ELT signal jamming the guard frequency.

Original NASA ASRS Text

Title: FGT ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative: DURING CHK IN WITH AGENCY RESPONSIBLE FOR SPECIAL AIRSPACE CTL, OUR FLT WAS CLRED ONTO RANGE AND GIVEN ALT CAP OF 30000' MSL. THIS ALT WAS STATED AS, '3-0-0,' BUT WAS UNDERSTOOD AS '3-3-0.' WHILE SETTING UP FOR A SUPERSONIC INTERCEPT WE CLBED TO FL300 AND ACCELERATED TO APPROX 1.3 MACH. AS THE ACFT PASSED APPROX MACH .98, THE PITOT/STATIC INS BEGAN TO FLUCTUATE +/- 2000' DUE TO THE SHOCKWAVE MOVING OVER THE STATIC PORTS ON THE ACFT. THIS CONTINUED AS THE ACFT ACCELERATED THROUGH MACH 1 WITH THE ALTIMETER STABILIZING NEAR 32000'. AS WE BELIEVED OUR AIRSPACE EXTENDED TO 33000', WE COMPLETED THE INTERCEPT AT THIS ALT. AFTER THE RUN OUR WINGMAN CALLED TO SAY THAT RANGE CTL HAD BEEN CALLING ON GUARD FREQ (243.0) TO ADVISE US OF OUR ALT EXCURSION. HOWEVER, WE WERE NOT MONITORING GUARD DUE TO AN ELT BEACON ON THAT FREQ. UPON DECELERATION BELOW MACK 1 ALTIMETER SHOWED 29500'. SUPERSONIC CRUISE IS A KNOWN PROB IN THE ACFT WITH RESPECT TO PITOT STATIC ERRORS. A LARGE ALT BUFFER IS REQUIRED WHEN CONDUCTING SUPERSONIC FLT OPS. CONTRIBUTING TO THE CONFUSION WAS A FALSE ELT SIGNAL JAMMING THE GUARD FREQ.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.