PA-46 Malibu Meridian
Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 100; Flight Crew Total 1500; Flight Crew Type 700
Communication Breakdown
ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Aircraft Equipment Problem Dissipated; Flight Crew Took Evasive Action
Aircraft; Human Factors
Experienced manifold pressure fluctuation at FL210 in cruise flight.  After several minutes; manifold pressure was steadily decreasing. [I] called Center to report a problem with no answer on last assigned frequency.  After several more attempts; as well as an attempt to contact them on 121.5 MHZ; all with no response; the manifold pressure was approaching a level where cabin pressurization could not be maintained.  Pilot in Command executed a descent from FL210 for lower altitude; while attempting to troubleshoot the problem and find the correct frequency for Center due to a missed handoff. After locating the correct Center frequency; and making contact with the Controller; I advised them of my altitude and reason for immediate descent from FL210.  I asked the Controller for an immediate descent to a lower altitude; while I troubleshot the manifold pressure problem.  They issued me a new clearance to FL160.  I also advised them that I was not handed off to the next Controller correctly; and the altitude deviation from FL210 was necessary to avoid a possible cabin pressurization emergency.  Manifold pressure was restored at the lower altitude and the flight was continued to the destination.Note: I was monitoring 121.5 MHZ during the entire flight; and did not hear any attempt from Center to contact me.
PA-46 pilot reports fluctuating manifold pressure at FL210 and the inability to contact ATC.  A descent is initiated before communications can be established due to the possibility of losing cabin pressurization.  At 16;000 feet MAP is normal and flight continues to destination.