Narrative:

Flight plan route clearance was issued, 'direct alcoa, cross alcoa 350,' then a vector of about 260 degrees was issued to go around a military airspace (during climb). After I cleared the military block, they cleared me direct alcoa flight plan route, cross alcoa at 350, 'can you make it?' I said yes, for at this time it didn't appear to be a problem. A little later ATC said, 'I have traffic, can you increase your rate of climb?' I gave it full climb power and pitched the nose up to 2000 FPM on the autoplt vertical rate control this was done at about 26000' and continued till out of 31000'. By now the airspeed was down to a little above velocity 0 flap. I switched to airspeed hold on the autoplt and continued the climb at 200-300 FPM. 10 mi (1 min at 200 FPM) I was out of 34600' a new voice came on from sfo ATC and said, 'you said you could make it.' I said, 'we're at 34800, is that ok?' then ATC stated,' if unable to cross alcoa at 350, make an immediate right turn to 070, company traffic 33.' so I said, 'roger, turning to 070 degrees, but I'll need lower to do this turn.' sfo said unable, air carrier TA 310. By now another minute had elapsed and my altimeter touched 35000'. We reported 350 and sfo cleared us on course. But now as I slowly turned back to course heading (5 degree bank) the airspeed sagged to velocity 0 flap and the 'G' load caused some prestall buffet. (I had disconnected the autoplt to start the turn to 070 degrees.) I left the altitude sag 400' (34600'), then with a little more speed rapidly climbed back to 35000'. No more was said. In retrospect, I wish I had known what altitude the traffic was at so the climb could have been planned more efficiently. I had originally planned to sacrifice my speed for altitude during the last 1500', which would have put me at alcoa at 35000', just a little above velocity 0 flap, with over 3000 mi of straight and level flying to accelerate back to cruise. Another option would have been ot use the 'pms' which I turned on a little later. The pms leveled the aircraft at 34750' at the time and weight it was turned on. I was under the assumption, ATC altitude (mode C) monitoring was +/-200'. Altimeter tolerance is +/-40' at sea level and 2% per 1000'. This would have give a worse case scenario of 520' clearance using 2000' sep. No traffic was observed or given.

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Original NASA ASRS Text

Title: ACR WDB ALT DEVIATION UNDERSHOT ALT CROSSING RESTRICTION AT START OF EXTENDED OVERWATER OPERATION.

Narrative: FLT PLAN RTE CLRNC WAS ISSUED, 'DIRECT ALCOA, CROSS ALCOA 350,' THEN A VECTOR OF ABOUT 260 DEGS WAS ISSUED TO GO AROUND A MIL AIRSPACE (DURING CLB). AFTER I CLRED THE MIL BLOCK, THEY CLRED ME DIRECT ALCOA FLT PLAN RTE, CROSS ALCOA AT 350, 'CAN YOU MAKE IT?' I SAID YES, FOR AT THIS TIME IT DIDN'T APPEAR TO BE A PROB. A LITTLE LATER ATC SAID, 'I HAVE TFC, CAN YOU INCREASE YOUR RATE OF CLB?' I GAVE IT FULL CLB PWR AND PITCHED THE NOSE UP TO 2000 FPM ON THE AUTOPLT VERT RATE CONTROL THIS WAS DONE AT ABOUT 26000' AND CONTINUED TILL OUT OF 31000'. BY NOW THE AIRSPD WAS DOWN TO A LITTLE ABOVE VELOCITY 0 FLAP. I SWITCHED TO AIRSPD HOLD ON THE AUTOPLT AND CONTINUED THE CLB AT 200-300 FPM. 10 MI (1 MIN AT 200 FPM) I WAS OUT OF 34600' A NEW VOICE CAME ON FROM SFO ATC AND SAID, 'YOU SAID YOU COULD MAKE IT.' I SAID, 'WE'RE AT 34800, IS THAT OK?' THEN ATC STATED,' IF UNABLE TO CROSS ALCOA AT 350, MAKE AN IMMEDIATE RIGHT TURN TO 070, COMPANY TFC 33.' SO I SAID, 'ROGER, TURNING TO 070 DEGS, BUT I'LL NEED LOWER TO DO THIS TURN.' SFO SAID UNABLE, ACR TA 310. BY NOW ANOTHER MINUTE HAD ELAPSED AND MY ALTIMETER TOUCHED 35000'. WE RPTED 350 AND SFO CLRED US ON COURSE. BUT NOW AS I SLOWLY TURNED BACK TO COURSE HDG (5 DEG BANK) THE AIRSPD SAGGED TO VELOCITY 0 FLAP AND THE 'G' LOAD CAUSED SOME PRESTALL BUFFET. (I HAD DISCONNECTED THE AUTOPLT TO START THE TURN TO 070 DEGS.) I LEFT THE ALT SAG 400' (34600'), THEN WITH A LITTLE MORE SPD RAPIDLY CLBED BACK TO 35000'. NO MORE WAS SAID. IN RETROSPECT, I WISH I HAD KNOWN WHAT ALT THE TFC WAS AT SO THE CLB COULD HAVE BEEN PLANNED MORE EFFICIENTLY. I HAD ORIGINALLY PLANNED TO SACRIFICE MY SPD FOR ALT DURING THE LAST 1500', WHICH WOULD HAVE PUT ME AT ALCOA AT 35000', JUST A LITTLE ABOVE VELOCITY 0 FLAP, WITH OVER 3000 MI OF STRAIGHT AND LEVEL FLYING TO ACCELERATE BACK TO CRUISE. ANOTHER OPTION WOULD HAVE BEEN OT USE THE 'PMS' WHICH I TURNED ON A LITTLE LATER. THE PMS LEVELED THE ACFT AT 34750' AT THE TIME AND WT IT WAS TURNED ON. I WAS UNDER THE ASSUMPTION, ATC ALT (MODE C) MONITORING WAS +/-200'. ALTIMETER TOLERANCE IS +/-40' AT SEA LEVEL AND 2% PER 1000'. THIS WOULD HAVE GIVE A WORSE CASE SCENARIO OF 520' CLRNC USING 2000' SEP. NO TFC WAS OBSERVED OR GIVEN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.