C550 pilot reported a loss of cabin pressure resulting in a diversion; subsequently departing back t...

Attributes
ACN	1678344
Time
Date	201908
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	Marginal
Light	Dawn
Aircraft 1
Make Model Name	Citation II S2/Bravo (C550)
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Commercial Flight Crew Flight Instructor Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 125 Flight Crew Total 5300 Flight Crew Type 1000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural FAR Deviation - Procedural Published Material / Policy

Narrative:

We experienced a depressurization at FL400. I [requested priority handling with ATC] followed by a descent to below 10;000 feet. We then landed at ZZZ. Inspection of the airplane did not reveal any structural damage. This was discussed with the co-owner of the plane who is also a mechanic and pilot with over 30;000 hours. He suggested that I fly the airplane back home unpressurized as allowed by the MEL. I agreed with him and filed a flight plan for 8;000 feet for the [next] morning. After uneventful preflight and startup we taxied to the runway. During takeoff at 90 knots IAS the airplane swerved to the left and vibrated due to a left main tire blowout. I was able to abort the takeoff and taxi the plane to the ramp. In my opinion these 2 events were not related. My concern after talking to the owner/mechanic again is that the MEL for unpressurized flight may not have been valid since the airplane was recently purchased. The MEL was resubmitted after purchase; but may still be in process with the FAA. For this reason it is possible that I unintentionally violated a regulation.

Original NASA ASRS Text

Title: C550 pilot reported a loss of cabin pressure resulting in a diversion; subsequently departing back to home airport; possibly with an incorrect MEL.

Narrative: We experienced a depressurization at FL400. I [requested priority handling with ATC] followed by a descent to below 10;000 feet. We then landed at ZZZ. Inspection of the airplane did not reveal any structural damage. This was discussed with the co-owner of the plane who is also a Mechanic and pilot with over 30;000 hours. He suggested that I fly the airplane back home unpressurized as allowed by the MEL. I agreed with him and filed a flight plan for 8;000 feet for the [next] morning. After uneventful preflight and startup we taxied to the runway. During takeoff at 90 knots IAS the airplane swerved to the left and vibrated due to a left main tire blowout. I was able to abort the takeoff and taxi the plane to the ramp. In my opinion these 2 events were not related. My concern after talking to the owner/mechanic again is that the MEL for unpressurized flight may not have been valid since the airplane was recently purchased. The MEL was resubmitted after purchase; but may still be in process with the FAA. For this reason it is possible that I unintentionally violated a regulation.

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.