<< >> NASA ASRS Report 390223, January 1998

An air carrier DC9 climbing to FL350 experiences speed reduction and slight vibration passing through FL343. The pilot was unable to maintain altitude and began a descent to recover airspeed resulting in a conflict with another aircraft.

Attributes
ACN	390223
Time
Date	199801
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zhu
State Reference	TX
Altitude	msl bound lower : 34000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu artcc : zny
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 6500
ASRS Report	390223
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe non adherence : required legal separation non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable
Consequence	Other
Miss Distance	horizontal : 18000 vertical : 1300
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

We were climbing to FL330 and were leaving FL315 ft when ZHU asked us if we could reach FL350 in 4 mins. According to the weight of the aircraft, it was decided that it was possible and we accepted FL350. When passing through approximately FL343, the center asked if we had reached FL350, to which we answered that we had almost reached it. When at approximately FL340 with the required climb rate, the speed began to reduce and a light vibration was felt as if we were approaching a stall, for which reason we leveled the aircraft to recover speed. However the vibration continued and the speed continued to reduce, for which reason a descent was begun to recover the speed. There was a conflict with another traffic resulting in a resolution alert of the TCAS (reduce your descent) iv TCASII.

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Original NASA ASRS Text

Title: AN ACR DC9 CLBING TO FL350 EXPERIENCES SPD REDUCTION AND SLIGHT VIBRATION PASSING THROUGH FL343. THE PLT WAS UNABLE TO MAINTAIN ALT AND BEGAN A DSCNT TO RECOVER AIRSPD RESULTING IN A CONFLICT WITH ANOTHER ACFT.

Narrative: WE WERE CLBING TO FL330 AND WERE LEAVING FL315 FT WHEN ZHU ASKED US IF WE COULD REACH FL350 IN 4 MINS. ACCORDING TO THE WT OF THE ACFT, IT WAS DECIDED THAT IT WAS POSSIBLE AND WE ACCEPTED FL350. WHEN PASSING THROUGH APPROX FL343, THE CTR ASKED IF WE HAD REACHED FL350, TO WHICH WE ANSWERED THAT WE HAD ALMOST REACHED IT. WHEN AT APPROX FL340 WITH THE REQUIRED CLB RATE, THE SPD BEGAN TO REDUCE AND A LIGHT VIBRATION WAS FELT AS IF WE WERE APCHING A STALL, FOR WHICH REASON WE LEVELED THE ACFT TO RECOVER SPD. HOWEVER THE VIBRATION CONTINUED AND THE SPD CONTINUED TO REDUCE, FOR WHICH REASON A DSCNT WAS BEGUN TO RECOVER THE SPD. THERE WAS A CONFLICT WITH ANOTHER TFC RESULTING IN A RESOLUTION ALERT OF THE TCAS (REDUCE YOUR DSCNT) IV TCASII.

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.