On takeoff roll both engine bleed valves failed to the emergency position.

Attributes
ACN	342248
Time
Date	199607
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bhm
State Reference	AL
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air taxi
Make Model Name	Learjet 35
Operating Under FAR Part	Part 135
Flight Phase	other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : cfi
Experience	flight time last 90 days : 100 flight time total : 1900 flight time type : 25
ASRS Report	342248
Person 2
Affiliation	company : air taxi
Function	flight crew : captain
Qualification	pilot : cfi pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 45 flight time total : 4300 flight time type : 1300
ASRS Report	342247
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other other : unspecified cockpit
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

After a part 91 stage leg XXX-ZZZ to pick up 6 passenger for part 135 trip ZZZ-BBB, the leg to BBB was delayed approximately 1 hour due to WX being below minimums at BBB. WX lifted, aircraft started taxi to runway 5 at ZZZ. Checklists/briefs conducted, all normal. Cleared for takeoff runway 5, power applied then noticed air noise of pressurization louder than normal. Power then was brought back to idle. Pilot and I talked about it and bleed air/cabin air valves reset. Takeoff power applied again, all seemed/sounded normal. During takeoff roll the bleed valves went into emergency position. After gear retraction light smoke was filling the cockpit/cabin, smelled like jet engine exhaust. Also heat was felt as this is normal when the system goes into emergency mode. The smoke was of concern. It was never heavy enough to don oxygen mask or goggles. Abnormal checklist accomplished, shut off both bleeds and cabin air. Declared an emergency and returned to land after dumping approximately 800 pounds of fuel. We spoke to our maintenance department and recycled valves. At this point all passenger were unloaded and the part 135 leg of ZZZ-BBB was canceled. Aircraft was flown back to XXX part 91 with no problems. Callback conversation with reporter revealed the following information: analyst contacted the reporter who related the following narrative. After return to the field I contacted our operations base maintenance and was advised to return with the bleed valves and air-conditioning in off position. Return flight was made with bleeds and air-conditioning off. I and PF did not understand what caused both bleed valves to fail to the emergency position. I have no knowledge of any maintenance performed or components replaced to correct the bleed problem. The aircraft manufacturer's representative advised me the light smoke or vapor was residual dust or light oil coating in the pneumatic ducts. There was no previous history on this airplane of pneumatic failure. The FAA ddi not contact the reporter.

Original NASA ASRS Text

Title: ON TKOF ROLL BOTH ENG BLEED VALVES FAILED TO THE EMER POS.

Narrative: AFTER A PART 91 STAGE LEG XXX-ZZZ TO PICK UP 6 PAX FOR PART 135 TRIP ZZZ-BBB, THE LEG TO BBB WAS DELAYED APPROX 1 HR DUE TO WX BEING BELOW MINIMUMS AT BBB. WX LIFTED, ACFT STARTED TAXI TO RWY 5 AT ZZZ. CHKLISTS/BRIEFS CONDUCTED, ALL NORMAL. CLRED FOR TKOF RWY 5, PWR APPLIED THEN NOTICED AIR NOISE OF PRESSURIZATION LOUDER THAN NORMAL. PWR THEN WAS BROUGHT BACK TO IDLE. PLT AND I TALKED ABOUT IT AND BLEED AIR/CABIN AIR VALVES RESET. TKOF PWR APPLIED AGAIN, ALL SEEMED/SOUNDED NORMAL. DURING TKOF ROLL THE BLEED VALVES WENT INTO EMER POS. AFTER GEAR RETRACTION LIGHT SMOKE WAS FILLING THE COCKPIT/CABIN, SMELLED LIKE JET ENG EXHAUST. ALSO HEAT WAS FELT AS THIS IS NORMAL WHEN THE SYS GOES INTO EMER MODE. THE SMOKE WAS OF CONCERN. IT WAS NEVER HVY ENOUGH TO DON OXYGEN MASK OR GOGGLES. ABNORMAL CHKLIST ACCOMPLISHED, SHUT OFF BOTH BLEEDS AND CABIN AIR. DECLARED AN EMER AND RETURNED TO LAND AFTER DUMPING APPROX 800 LBS OF FUEL. WE SPOKE TO OUR MAINT DEPT AND RECYCLED VALVES. AT THIS POINT ALL PAX WERE UNLOADED AND THE PART 135 LEG OF ZZZ-BBB WAS CANCELED. ACFT WAS FLOWN BACK TO XXX PART 91 WITH NO PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ANALYST CONTACTED THE RPTR WHO RELATED THE FOLLOWING NARRATIVE. AFTER RETURN TO THE FIELD I CONTACTED OUR OPS BASE MAINT AND WAS ADVISED TO RETURN WITH THE BLEED VALVES AND AIR-CONDITIONING IN OFF POS. RETURN FLT WAS MADE WITH BLEEDS AND AIR-CONDITIONING OFF. I AND PF DID NOT UNDERSTAND WHAT CAUSED BOTH BLEED VALVES TO FAIL TO THE EMER POS. I HAVE NO KNOWLEDGE OF ANY MAINT PERFORMED OR COMPONENTS REPLACED TO CORRECT THE BLEED PROB. THE ACFT MANUFACTURER'S REPRESENTATIVE ADVISED ME THE LIGHT SMOKE OR VAPOR WAS RESIDUAL DUST OR LIGHT OIL COATING IN THE PNEUMATIC DUCTS. THERE WAS NO PREVIOUS HISTORY ON THIS AIRPLANE OF PNEUMATIC FAILURE. THE FAA DDI NOT CONTACT THE RPTR.

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.