LR35 ACFT ON TEST FLT FOR STALL CHARACTERISTICS; FLC REQUESTED AND RECEIVED A BLOCK ALT; BUT DURING STALL LOST MORE ALT THAN THE BLOCK. AFTER FLC REQUESTED LOWER ALT CTLR COULDN'T APPROVE DUE TO TFC; BUT RPTR ACFT HAD TO DSND DUE TO LOW AIRSPD.

Narrative

ASSIGNED BLOCK FL410-370 FOR HIGH ALT STALL CHARACTERISTIC EVALUATION. ACFT WAS LOADED TO AFT CTR OF GRAVITY; HVY WT OP TEST CONDITION REQUIREMENTS. PRIOR REVIEW OF PROJECTED PERFORMANCE CAPABILITY INDICATED AN ADEQUATE MARGIN FOR RECOVERY IN THE BLOCK SHOULD BE AVAILABLE. STALL WAS INITIATED FROM A TRIM SPD OF 1.3 VSI AT APPROX FL400. RECOVERY WAS INITIATED WITH MAX THRUST AT PUSHERS ACTIVATION AT AN APPROX ALT OF FL397. AT FL390 IT BECAME APPARENT THE ACFT WOULD NOT ACCELERATE TO PERMIT LEVEL FLT AT FL370. THE CTLR WAS IMMEDIATELY ADVISED OF THE SIT. HE STATED WE HAD TO MAINTAIN FL370 TO WHICH WE RESPONDED WE WERE UNABLE TO MAINTAIN LEVEL FLT. HE AGAIN SAID WE COULD NOT DSND BELOW FL370. WE RPTED AGAIN WE WERE UNABLE TO MAINTAIN LEVEL FLT. BY THIS POINT WE WERE DSNDING BELOW FL370 AT A RATE OF APPROX 100-200 FPM. THE CTLR THEN GAVE US A 90 DEG TURN (WHICH FURTHER MADE THE ALT ISSUE MORE DIFFICULT). LATER HE TOLD US WE COULD MAINTAIN OUR CURRENT ALT (THEN FL355) WHEN ALLOWED US TO ACCELERATE AND RESUME NORMAL FLT. THE CTLR INDICATED THE REASON WE COULDN'T DSND BECAUSE OF OTHER TFC. AFTER ALL WAS DONE AND WE HAD RETURNED TO OUR BLOCK; HE ADVISED US ON RADIO HE WOULD PROCESS AS A 'POSSIBLE PLT DEV.'