Narrative:

First officer was PF at FL250 to mci with autoplt engaged. Approximately 160 NM south of mci, ATC cleared flight from FL250 to FL240 (1000 ft descent). Altitude was inserted into altitude alerter, company altitude awareness procedure was followed, and first officer executed the descent via the autoplt pitch control wheel. During the descent, #1 flight attendant called cockpit on the interphone, which was answered by PNF, captain. Captain's discussion with flight attendant was brief (15-20 seconds) regarding cabin temperature conditions and the visual health of 1 passenger who appeared grayish in color. This conversation was followed shortly thereafter with coded knock on cockpit door. The captain (PNF) glanced at the altimeter to verify PF's altitude, which was within 300 ft of the FL240 leveloff altitude, and proceeded to unbuckle, stand, and remove the katy bar on the cockpit door. Simultaneously, as the cockpit door was opened, captain looked back at the first officer's altimeter and stated, '(name) FL240' just prior to the altitude alerter's 300 ft below selected altitude chime sounded. First officer immediately disconnected the autoplt and initiated a climb to correct for the error. In the transition, an additional 200 ft of altitude was lost (23500 ft indicated) before a positive climb was established and aircraft was leveled at FL240. During the maneuver to return to FL240, there were no TA or RA traffic depicted, and no evasive action called for by the onboard TCASII. Both the captain and first officer were distracted by a number of factors that contributed to this incident. Aircraft was dispatched with 1 air-conditioning pack inoperative. The left pack, which provides conditioned air to the cockpit, was inoperative and airflow provided by the operative right pack to the cockpit was minimal. Given the fact that departure airport ground temperature was 34 degrees C, no conditioned air cart was planned for nor provided at the gate. Our normal ground time is 30 mins, but an additional 20 min delay occurred due to actual fuel load being 1000 pounds less than our release. Cabin temperature at time of pushback/takeoff was 99 degrees F with cockpit temperature estimated at 10-15 degrees higher -- 1 operable air-conditioning pack will not cool the cabin nor cockpit adequately in this condition. At the time of the incident, estimated cockpit temperature was minimum 90 degrees F with virtually no airflow and we were miserable. Overall stress levels increased while the mental and physical well-being of the flight deck crew slowly deteriorated (increasing tiredness and irritability were primary symptoms). Under the environmental conditions we were subjected to, it didn't take long to determine that pilot incapacitation could be a serious outcome based on individual tolerance to the heat. Chain of events ultimately led to this altitude deviation. Hindsight being 20/20, could have been better not to dispatch this aircraft during the heat of the summer day.

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Original NASA ASRS Text

Title: ALT OVERSHOT DUE TO DISTR OF UNCOMFORTABLE FLC OF A DC9 THAT HAD PAX HEALTH PROBS DUE TO HIGH CABIN COCKPIT TEMPS OUT OF SAT, TX.

Narrative: FO WAS PF AT FL250 TO MCI WITH AUTOPLT ENGAGED. APPROX 160 NM S OF MCI, ATC CLRED FLT FROM FL250 TO FL240 (1000 FT DSCNT). ALT WAS INSERTED INTO ALT ALERTER, COMPANY ALT AWARENESS PROC WAS FOLLOWED, AND FO EXECUTED THE DSCNT VIA THE AUTOPLT PITCH CTL WHEEL. DURING THE DSCNT, #1 FLT ATTENDANT CALLED COCKPIT ON THE INTERPHONE, WHICH WAS ANSWERED BY PNF, CAPT. CAPT'S DISCUSSION WITH FLT ATTENDANT WAS BRIEF (15-20 SECONDS) REGARDING CABIN TEMP CONDITIONS AND THE VISUAL HEALTH OF 1 PAX WHO APPEARED GRAYISH IN COLOR. THIS CONVERSATION WAS FOLLOWED SHORTLY THEREAFTER WITH CODED KNOCK ON COCKPIT DOOR. THE CAPT (PNF) GLANCED AT THE ALTIMETER TO VERIFY PF'S ALT, WHICH WAS WITHIN 300 FT OF THE FL240 LEVELOFF ALT, AND PROCEEDED TO UNBUCKLE, STAND, AND REMOVE THE KATY BAR ON THE COCKPIT DOOR. SIMULTANEOUSLY, AS THE COCKPIT DOOR WAS OPENED, CAPT LOOKED BACK AT THE FO'S ALTIMETER AND STATED, '(NAME) FL240' JUST PRIOR TO THE ALT ALERTER'S 300 FT BELOW SELECTED ALT CHIME SOUNDED. FO IMMEDIATELY DISCONNECTED THE AUTOPLT AND INITIATED A CLB TO CORRECT FOR THE ERROR. IN THE TRANSITION, AN ADDITIONAL 200 FT OF ALT WAS LOST (23500 FT INDICATED) BEFORE A POSITIVE CLB WAS ESTABLISHED AND ACFT WAS LEVELED AT FL240. DURING THE MANEUVER TO RETURN TO FL240, THERE WERE NO TA OR RA TFC DEPICTED, AND NO EVASIVE ACTION CALLED FOR BY THE ONBOARD TCASII. BOTH THE CAPT AND FO WERE DISTRACTED BY A NUMBER OF FACTORS THAT CONTRIBUTED TO THIS INCIDENT. ACFT WAS DISPATCHED WITH 1 AIR-CONDITIONING PACK INOP. THE L PACK, WHICH PROVIDES CONDITIONED AIR TO THE COCKPIT, WAS INOP AND AIRFLOW PROVIDED BY THE OPERATIVE R PACK TO THE COCKPIT WAS MINIMAL. GIVEN THE FACT THAT DEP ARPT GND TEMP WAS 34 DEGS C, NO CONDITIONED AIR CART WAS PLANNED FOR NOR PROVIDED AT THE GATE. OUR NORMAL GND TIME IS 30 MINS, BUT AN ADDITIONAL 20 MIN DELAY OCCURRED DUE TO ACTUAL FUEL LOAD BEING 1000 LBS LESS THAN OUR RELEASE. CABIN TEMP AT TIME OF PUSHBACK/TKOF WAS 99 DEGS F WITH COCKPIT TEMP ESTIMATED AT 10-15 DEGS HIGHER -- 1 OPERABLE AIR-CONDITIONING PACK WILL NOT COOL THE CABIN NOR COCKPIT ADEQUATELY IN THIS CONDITION. AT THE TIME OF THE INCIDENT, ESTIMATED COCKPIT TEMP WAS MINIMUM 90 DEGS F WITH VIRTUALLY NO AIRFLOW AND WE WERE MISERABLE. OVERALL STRESS LEVELS INCREASED WHILE THE MENTAL AND PHYSICAL WELL-BEING OF THE FLT DECK CREW SLOWLY DETERIORATED (INCREASING TIREDNESS AND IRRITABILITY WERE PRIMARY SYMPTOMS). UNDER THE ENVIRONMENTAL CONDITIONS WE WERE SUBJECTED TO, IT DIDN'T TAKE LONG TO DETERMINE THAT PLT INCAPACITATION COULD BE A SERIOUS OUTCOME BASED ON INDIVIDUAL TOLERANCE TO THE HEAT. CHAIN OF EVENTS ULTIMATELY LED TO THIS ALTDEV. HINDSIGHT BEING 20/20, COULD HAVE BEEN BETTER NOT TO DISPATCH THIS ACFT DURING THE HEAT OF THE SUMMER DAY.

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.