Commuter type light transport blows both main wheels upon landing at bna.

Attributes
ACN	164170
Time
Date	199011
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bna
State Reference	TN
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	landing other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 2950 flight time type : 200
ASRS Report	164170
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 8000 flight time type : 100
Events
Anomaly	aircraft equipment problem : critical non adherence other other anomaly other
Independent Detector	other flight crewa other other : unspecified
Resolutory Action	none taken : unable
Consequence	faa : investigated other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

The commuter light transport has a history of above normal brake system pressures (above 2000 psi). A procedure used by pilots of this aircraft type is to lightly tap the brake pedal and exercise the parking brake to relieve the high pressure. I believe this procedure caused the brakes to lock up en route from tcl to bna. On T/D, as weight was xferred to the main gears, both main tires blew out. The aircraft was stopped on the runway with no injuries or damage to the aircraft other than the tires and wheel assemblies. I believe there is some form of system problem with the light transport the ability of the brake hydraulic system to retain higher than normal system pressure should be reviewed and corrected. I further believe pilots should not exercise the brake system prior to landing (until this problem is resolved). I know I will not touch the brakes on the light transport until the aircraft is rolling out. Callback conversation with reporter revealed the following information. During callback reporter indicated that he is an aeronautical engineer with specific knowledge in hydraulics. The reporter alleges that brake system overpressures are experienced when a high system demand event (such as raising the landing gear and flaps) causes the variable displacement hydraulic pumps to deliver 'surge' pressure. This overpressure is trapped in the normal and emergency brake system by the nonreturn valve: neither system is apparently fitted with an overpressure relief valve. The reporter was concerned that this overpressure could affect seals and overall system integrity, thus he utilized the procedure of exercising the brakes in flight to relieve the overpressure. The reporter claims that some sort of system anomaly exits that will lock the brakes when thus exercised, and that the most likely culprit is the brake system priority shuttle valve. The reporter further claims that he is absolutely sure that the flight did not land with the parking brake set. The FAA investigated the incident (as has the airline) and have stated that the brakes should not be exercised in flight. The FAA is not proceeding with any enforcement action against the flight crew.

Original NASA ASRS Text

Title: COMMUTER TYPE LTT BLOWS BOTH MAIN WHEELS UPON LNDG AT BNA.

Narrative: THE COMMUTER LTT HAS A HISTORY OF ABOVE NORMAL BRAKE SYS PRESSURES (ABOVE 2000 PSI). A PROC USED BY PLTS OF THIS ACFT TYPE IS TO LIGHTLY TAP THE BRAKE PEDAL AND EXERCISE THE PARKING BRAKE TO RELIEVE THE HIGH PRESSURE. I BELIEVE THIS PROC CAUSED THE BRAKES TO LOCK UP ENRTE FROM TCL TO BNA. ON T/D, AS WEIGHT WAS XFERRED TO THE MAIN GEARS, BOTH MAIN TIRES BLEW OUT. THE ACFT WAS STOPPED ON THE RWY WITH NO INJURIES OR DAMAGE TO THE ACFT OTHER THAN THE TIRES AND WHEEL ASSEMBLIES. I BELIEVE THERE IS SOME FORM OF SYS PROB WITH THE LTT THE ABILITY OF THE BRAKE HYD SYS TO RETAIN HIGHER THAN NORMAL SYS PRESSURE SHOULD BE REVIEWED AND CORRECTED. I FURTHER BELIEVE PLTS SHOULD NOT EXERCISE THE BRAKE SYS PRIOR TO LNDG (UNTIL THIS PROB IS RESOLVED). I KNOW I WILL NOT TOUCH THE BRAKES ON THE LTT UNTIL THE ACFT IS ROLLING OUT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. DURING CALLBACK RPTR INDICATED THAT HE IS AN AERONAUTICAL ENGINEER WITH SPECIFIC KNOWLEDGE IN HYDS. THE RPTR ALLEGES THAT BRAKE SYS OVERPRESSURES ARE EXPERIENCED WHEN A HIGH SYS DEMAND EVENT (SUCH AS RAISING THE LNDG GEAR AND FLAPS) CAUSES THE VARIABLE DISPLACEMENT HYD PUMPS TO DELIVER 'SURGE' PRESSURE. THIS OVERPRESSURE IS TRAPPED IN THE NORMAL AND EMER BRAKE SYS BY THE NONRETURN VALVE: NEITHER SYS IS APPARENTLY FITTED WITH AN OVERPRESSURE RELIEF VALVE. THE RPTR WAS CONCERNED THAT THIS OVERPRESSURE COULD AFFECT SEALS AND OVERALL SYS INTEGRITY, THUS HE UTILIZED THE PROC OF EXERCISING THE BRAKES IN FLT TO RELIEVE THE OVERPRESSURE. THE RPTR CLAIMS THAT SOME SORT OF SYS ANOMALY EXITS THAT WILL LOCK THE BRAKES WHEN THUS EXERCISED, AND THAT THE MOST LIKELY CULPRIT IS THE BRAKE SYS PRIORITY SHUTTLE VALVE. THE RPTR FURTHER CLAIMS THAT HE IS ABSOLUTELY SURE THAT THE FLT DID NOT LAND WITH THE PARKING BRAKE SET. THE FAA INVESTIGATED THE INCIDENT (AS HAS THE AIRLINE) AND HAVE STATED THAT THE BRAKES SHOULD NOT BE EXERCISED IN FLT. THE FAA IS NOT PROCEEDING WITH ANY ENFORCEMENT ACTION AGAINST THE FLT CREW.

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.