A lancair LNC4 door window developed a six inch crack at FL240 and depressurized. The pilot had diff...

Narrative:

As I was traveling in a experimental lancair iv-pt pressurized aircraft; I experienced a cabin depressurization at FL240. I contacted center and requested 'aircraft X needs to descend-lost pressurization'. I got no response; so I initiated a descent to 12;000FT. I then put on my oximizing cannula and opened the oxygen bottle valve. I then called center again (sorry I can't remember the time interval) and got no response. I believe at FL190 I made third request for a lower altitude due to a loss of pressurization. I was having a difficult time keeping the cannula in my nose and thought at one point I was getting light headed. The controller asked if I wanted to declare an emergency; I replied 'no I now have my oxygen mask on'. The controller requested I turn right 30 degrees and ident; but in the challenge of keeping the cannula in my nose and flying the plane (at this point I realized the electric elevator trim servo was inoperative) I turned 30 degrees left and idented. The controller instructed me to continue a left turn back to my original heading and ident; which I did. The entire flight was in visual meteorological conditions.I descended down to 12;000FT and gained my composure. I then had time to anaylse the situation and thought the door seal was the culprit; (I had realized when the cabin depressurized I could hear the air leaving from the cabin door) but after bleeding the air from it I realized that wasn't the problem. I then looked further back and saw a 6 inch long crack in the aft upper cabin door window. Once I saw this I requested and received a 180 degree turn back to my departure airport. I have ordered a new window and the factory has a new procedure of installing it; which is better than the original build manual.

Original NASA ASRS Text

Title: A Lancair LNC4 door window developed a six inch crack at FL240 and depressurized. The pilot had difficulty keeping his oxygen cannula on his face in place and calling ATC for a lower altitude but he was ultimately successful.

Narrative: As I was traveling in a experimental Lancair IV-PT pressurized aircraft; I experienced a cabin depressurization at FL240. I contacted center and requested 'Aircraft X needs to descend-lost pressurization'. I got no response; so I initiated a descent to 12;000FT. I then put on my oximizing cannula and opened the oxygen bottle valve. I then called Center again (sorry I can't remember the time interval) and got no response. I believe at FL190 I made third request for a lower altitude due to a loss of pressurization. I was having a difficult time keeping the cannula in my nose and thought at one point I was getting light headed. The controller asked if I wanted to declare an emergency; I replied 'no I now have my oxygen mask on'. The controller requested I turn right 30 degrees and ident; but in the challenge of keeping the cannula in my nose and flying the plane (at this point I realized the electric elevator trim servo was inoperative) I turned 30 degrees left and idented. The controller instructed me to continue a left turn back to my original heading and ident; which I did. The entire flight was in visual meteorological conditions.I descended down to 12;000FT and gained my composure. I then had time to anaylse the situation and thought the door seal was the culprit; (I had realized when the cabin depressurized I could hear the air leaving from the cabin door) but after bleeding the air from it I realized that wasn't the problem. I then looked further back and saw a 6 inch long crack in the aft upper cabin door window. Once I saw this I requested and received a 180 degree turn back to my departure airport. I have ordered a new window and the factory has a new procedure of installing it; which is better than the original build manual.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1280771
Time
Date	201507
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Lancair IV/IVP
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Door Window
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Instrument
Experience	Flight Crew Last 90 Days 8.4 Flight Crew Total 1111 Flight Crew Type 175
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Flight Deck / Cabin / Aircraft Event Illness

A lancair LNC4 door window developed a six inch crack at FL240 and depressurized. The pilot had difficulty keeping his oxygen cannula on his face in place and calling ATC for a lower altitude but he was ultimately successful.