I have a newly flying TSIO-550 powered IV-P with a persistent and nasty problem.  On takeoff roll the manifold pressure is steady at 38.4 in Hg and the fuel rate is steady at 43 gph.   The engine runs very good up to this point.  At 50 ft AGL the manifold pressure starts to run away.  If left unattended it will climb to 43 In Hg and the fuel rate will chase the manifold pressure and go to 54 gph at which time the engine starts belching black smoke and looses power.  We have never let it go past this condition but it appears the engine would likely stop running if left unattended.  The plane accelerates very good from 0 kts to 90 kts.  At 50 ft AGL the plane is at 120 kts.  I have inspected all of the pressure reference lines going to the boost controller , I have had the controller rebuilt by Main Turbo, and I have applied air pressure to the waste gate and it operates normally.  The very odd twist is the first few flights were very normal and manifold pressure was steady the entire time.  We fixed a heavy right wing by changing the wing incidence of both wings and the problem started on the very next test flight.  I have ordered a new controller and it should be available in the next few days.  We have also found that the manifold pressure wonders 0.3 in Hg in level flight and will decrease in a climb and increase in a decent by approximately 1.4 in Hg.  This is all happening between the airport altitude of 330 ft and 4500 ft while making laps around the airport.  The problem seems to be steadily  getting worse.  However having the engine quit making power at 50 AGL is pretty bad….so getting “worse” may not be to relevant.

Any ideas as to what is wrong?  This problem has stumped quite a few industry experts.

Craig Berland

N7VG  IV-P