Date: 201305
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: Mixed
Weather elements / visibility: Icing; 10
Light: Daylight
Aircraft: Baron 58/58TC
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Pitot-Static System
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Private
Human factors: Training / Qualification; Confusion; Human-Machine Interface; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: Climbing through 9;000 [FT] on the way to 15;000 and eventually FL180 in IMC; I noticed the airspeed deteriorating. I reduced angle of attack to increase airspeed and the climb became a 1;000 FPM descent. Airspeed did not increase at a commensurate rate for that amount of descent. My initial thought was that I was feeling the effects of a mountain wave. I crosschecked instruments with the GPS and determined that the airspeed indicator was inaccurate. I concluded Pitot Heat was added too late to melt some ice. Shortly thereafter I broke out on top. I continued the flight. As the climb continued the airspeed continued to decay and settled at about 80 KTS for the cruise. I concluded that the ice blockage was partial and in a position where the pitot heat was not effective. I tried 'alternate air;' but there was no change in the airspeed or altimeter. When descending the airspeed increased and I made an uneventful ILS approach to VMC and then a visual approach and landing. On final approach the airspeed appeared to be about normal. During cruise it seemed very difficult to maintain consistent altitude. And I noticed that pressure differential did not reach the max for a 58P of 3.9psi (which it had on a flight two weeks earlier) but settled in on 3.1. I did not link these facts together.[On the next flight] I ensured that all anti ice was turned on when cleared for takeoff and departed. Again the airspeed decayed as I was in IMC. I continued flight cross checking speed with GPS. Encountered light to moderate rime enroute at 15;000 FT for first half of flight. Again the pressure differential was 3.1 and altitude was difficult to maintain exactly at assigned level. Needle would blip up 100 FT in a fraction of a second and then back; or down a few hundred FT in a second or two requiring a climb back to altitude. Cross checked altimeter with GPS altitude and saw a wide variation; thousands of FT. Broke clear of the icing and continued in VMC. Upon descent; the airspeed increased with descent to a value that appeared normal on final approach. I now suspect a static leak inside the pressure vessel due to recent maintenance. The plane is currently in the shop to confirm the suspicion of a static leak.I had continued two flights with this degraded equipment creating a new pilot error (continued flight with a malfunction).




Synopsis: BE58 pilot initially attributed airspeed and altitude indication anomalies to environmental effects; but upon further assessment concluded that a static leak inside the pressure vessel was more likely.