Date: 201409
Local time of day: 1201-1800
Location: ZHU.ARTCC, TX
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: TBM 700/TBM 850
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Training
Flight phase: Descent
Airspace: Class A ZHU
ATC / advisory: Center ZHU
Aircraft component: Air/Ground Communication
Component problem: Design
Reporter organization: Personal
Reporter function: Trainee; Pilot Flying
Reporter qualification: Flight Crew Rotorcraft; Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Glider; Flight Crew Commercial; Flight Crew Flight Instructor
Human factors: Communication Breakdown
Second reporter function: Pilot Not Flying; Instructor
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: Simulated Emergency Descent I was taking 6 day recurrent training with a TBM 850 instructor. My instructor filed an IFR flight plan (from the air) in the vicinity of STV with Houston Center in order to climb on a heading to FL280 to practice a simulated emergency descent to 14;500. The practice simulated emergency descent procedure was approved by ATC with block altitudes and on a heading via radar vectors. I was in the left seat and my instructor was in the right seat. My instructor called out simulated 'master alarm' and 'Cabin Pressure' on the CAS; I identified the problem and we both donned oxygen masks; had our headsets on and switched the headset microphone to the oxygen mask transmit position. Due to oxygen breathing noise; it was hard for me to hear my own voice because of breathing feedback. The instructor had agreed to handle all radio communications during my recurrent training. My instructor filed the IFR flight plan for the simulated emergency descent procedure. I reasonably expected him to continue using the radio to communicate with ATC. This was the understanding between us. The instructor thought he communicated with ATC that we were starting the procedure and vacating FL280; but (not known to us) the microphone in the instructor's oxygen mask did not work so ATC did not hear the instructor's radio transmission. We started the procedure and vacated FL280 for 14;000. We started down and when passing through FL270 ATC questioned our descent. We leveled off and climbed back to FL280. The controller said he did not hear our request to start the simulated emergency descent and to start down (vacate FL280). We explained to ATC what had happened. Then we requested to start the simulated emergency descent procedure with ATC and descended from FL280 to 14;500 without incident and terminated the simulated emergency descent maneuver and canceled IFR with Houston Center.


Second narrative: Training for proper use of emergency equipment for emergency descent. We were vectored to an area to do training for the procedure and when the exercise was initiated we were donning the equipment to establish communications with ATC and on the intercom and the autopilot was selected off to prepare the descent. The distraction of the cabin noise and oxygen mask application during the communication that was being transmitted but was not confirmed with ATC; and we started to descend. I caught the descent and returned to the altitude and then we got the confirmation to descend to complete the maneuver. We had trained and prepared previously in detail for the maneuver. I had asked for the vector and received that to airspace that was out of the way. A flurry of ATC communication with other aircraft and microphone in the mask noise made the ATC acknowledgment difficult. The next training event I will be sure of the clarification before on the normal headsets instead of on the mask microphones.


Synopsis: TBM850 instructor and student plan and request a practice emergency descent from ATC; starting from FL280. Oxygen mask noise prevents proper communication with ATC and the descent is initiated without approval.