Narrative:

The sea class B airspace contains a floor at 1100 ft MSL that overlays the south 3/4 of bfi runway 13R. 2 nights ago I was giving instruction to a private pilot. He had completed a practice ILS 13R approach at bfi and was cleared for an early left crosswind for a VFR transition into rnt. He climbed at vy to about 1500 MSL and missed the floor, i.e. Did not penetrate the class B airspace, but during the postflt discussion I realized he was not aware of the 1100 ft floor and discussed it with him, stressing the importance of staying well below it on straight departures from 13R (stay at 900 ft till south of the airport boundary). Tonight I was flying a practice approach to the same runway. I requested the option, and then an early crosswind to rnt. I was cleared for the option and told to remain outside the seattle class B airspace. Because of this, I expected a straight out departure and planned to climb to no more than 900 ft, to remain below the 1100 ft floor. Another aircraft was negotiating an intersection departure, and I was then cleared for a full stop and to hold position the runway. I asked if I was cleared for a touch and go, and was cleared for it, while the other aircraft held short. I was then cleared for an early crosswind. There is a ridge to the east of bfi. I climbed at about 500 FPM targeting the 900 ft altitude for a straight out and crossed the ridge at about 800 ft. This is too low, because the ridge is a congested area. Although I was distracted by the tower controller I should have revised my planned altitude to accommodate the crosswind departure. I also think I fixated on the 1110 ft floor because of my discussion 2 nights earlier.

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Original NASA ASRS Text

Title: LOW FLT THAT IS CONSIDERED TO BE CTLED FLT INTO TERRAIN IN A NIGHT OP.

Narrative: THE SEA CLASS B AIRSPACE CONTAINS A FLOOR AT 1100 FT MSL THAT OVERLAYS THE S 3/4 OF BFI RWY 13R. 2 NIGHTS AGO I WAS GIVING INSTRUCTION TO A PVT PLT. HE HAD COMPLETED A PRACTICE ILS 13R APCH AT BFI AND WAS CLRED FOR AN EARLY L XWIND FOR A VFR TRANSITION INTO RNT. HE CLBED AT VY TO ABOUT 1500 MSL AND MISSED THE FLOOR, I.E. DID NOT PENETRATE THE CLASS B AIRSPACE, BUT DURING THE POSTFLT DISCUSSION I REALIZED HE WAS NOT AWARE OF THE 1100 FT FLOOR AND DISCUSSED IT WITH HIM, STRESSING THE IMPORTANCE OF STAYING WELL BELOW IT ON STRAIGHT DEPS FROM 13R (STAY AT 900 FT TILL S OF THE ARPT BOUNDARY). TONIGHT I WAS FLYING A PRACTICE APCH TO THE SAME RWY. I REQUESTED THE OPTION, AND THEN AN EARLY XWIND TO RNT. I WAS CLRED FOR THE OPTION AND TOLD TO REMAIN OUTSIDE THE SEATTLE CLASS B AIRSPACE. BECAUSE OF THIS, I EXPECTED A STRAIGHT OUT DEP AND PLANNED TO CLB TO NO MORE THAN 900 FT, TO REMAIN BELOW THE 1100 FT FLOOR. ANOTHER ACFT WAS NEGOTIATING AN INTXN DEP, AND I WAS THEN CLRED FOR A FULL STOP AND TO HOLD POS THE RWY. I ASKED IF I WAS CLRED FOR A TOUCH AND GO, AND WAS CLRED FOR IT, WHILE THE OTHER ACFT HELD SHORT. I WAS THEN CLRED FOR AN EARLY XWIND. THERE IS A RIDGE TO THE E OF BFI. I CLBED AT ABOUT 500 FPM TARGETING THE 900 FT ALT FOR A STRAIGHT OUT AND CROSSED THE RIDGE AT ABOUT 800 FT. THIS IS TOO LOW, BECAUSE THE RIDGE IS A CONGESTED AREA. ALTHOUGH I WAS DISTRACTED BY THE TWR CTLR I SHOULD HAVE REVISED MY PLANNED ALT TO ACCOMMODATE THE XWIND DEP. I ALSO THINK I FIXATED ON THE 1110 FT FLOOR BECAUSE OF MY DISCUSSION 2 NIGHTS EARLIER.

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.