GA small transport altitude deviation undershot crossing restriction.

Attributes
ACN	80386
Time
Date	198801
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : apa
State Reference	CO
Altitude	msl bound lower : 16000 msl bound upper : 19000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdv
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 50 flight time total : 2100 flight time type : 40
ASRS Report	80386
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : crossing restriction not met non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	none taken : anomaly accepted none taken : detected after the fact none taken : unable
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

En route from sck to apa at FL250 heater quit with 1 1/2 hours to go. Became colder but nowhere near debilitating. Nevertheless, definitely a preoccupation. Thought about advising controllers at slc or den center about situation but didn't think it would cause a problem. Cleared to descended and then to byson intersection, I thought to cross byson at or above 16000'. I'm fairly certain that I read it back that way. After byson, I was handed off to the next controller who said that the previous one wanted to know why I had not crossed at 16000'. I told him that I thought I was to cross at or above. Then, approaching the airport, I noticed that the lights on my avionics were off. Because of the cold I had put on a sport jacket and then a massive, bulky overcoat. A buckle on the coat had snagged the avionics master switch and turned the avionics off. I turned them back on and asked approach if he had been trying to get me and he replied affirmatively. Things would have been a lot easier if I had notified the controller when the heater failed. It would have not only alerted ATC, but I think it would have raised my own awareness that this was, indeed, an unusual situation that required extra vigilance.

Original NASA ASRS Text

Title: GA SMT ALT DEVIATION UNDERSHOT CROSSING RESTRICTION.

Narrative: ENRTE FROM SCK TO APA AT FL250 HEATER QUIT WITH 1 1/2 HRS TO GO. BECAME COLDER BUT NOWHERE NEAR DEBILITATING. NEVERTHELESS, DEFINITELY A PREOCCUPATION. THOUGHT ABOUT ADVISING CTLRS AT SLC OR DEN CENTER ABOUT SITUATION BUT DIDN'T THINK IT WOULD CAUSE A PROB. CLRED TO DESCENDED AND THEN TO BYSON INTXN, I THOUGHT TO CROSS BYSON AT OR ABOVE 16000'. I'M FAIRLY CERTAIN THAT I READ IT BACK THAT WAY. AFTER BYSON, I WAS HANDED OFF TO THE NEXT CTLR WHO SAID THAT THE PREVIOUS ONE WANTED TO KNOW WHY I HAD NOT CROSSED AT 16000'. I TOLD HIM THAT I THOUGHT I WAS TO CROSS AT OR ABOVE. THEN, APCHING THE ARPT, I NOTICED THAT THE LIGHTS ON MY AVIONICS WERE OFF. BECAUSE OF THE COLD I HAD PUT ON A SPORT JACKET AND THEN A MASSIVE, BULKY OVERCOAT. A BUCKLE ON THE COAT HAD SNAGGED THE AVIONICS MASTER SWITCH AND TURNED THE AVIONICS OFF. I TURNED THEM BACK ON AND ASKED APCH IF HE HAD BEEN TRYING TO GET ME AND HE REPLIED AFFIRMATIVELY. THINGS WOULD HAVE BEEN A LOT EASIER IF I HAD NOTIFIED THE CTLR WHEN THE HEATER FAILED. IT WOULD HAVE NOT ONLY ALERTED ATC, BUT I THINK IT WOULD HAVE RAISED MY OWN AWARENESS THAT THIS WAS, INDEED, AN UNUSUAL SITUATION THAT REQUIRED EXTRA VIGILANCE.

Data retrieved from NASA's ASRS site as of August 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.