Narrative:

We were conducting the lda-DME approach to runway 18 at dca in variable IFR conditions, with rainshowers in the vicinity and with the potomac river in sight as we passed below about 1500 ft MSL. By that time we were in landing confign with all checklists and SOP's accomplished and the missed approach altitude 1800 ft set in the altitude reminder. At about 1200 ft MSL the captain disconnected the autoplt, as we were in what appeared to be improved conditions below the majority of the clouds, and we continued toward the 720 ft MSL MDA on localizer and GS. At about 1000 ft the tower controller advised that a heavy rainshower had just moved over the field and asked if we could see the airport. I advised that we could not. At the MDA the captain initiated the missed approach with toga thrust and a pitch up. Wing flaps were called for position 1 and I selected position 1 and then with a positive rate of climb the gear was called up, which I then selected up. I advised the tower that we had missed to which the tower instructed us to fly the 185 radial (published miss-dca 185). Within seconds the GPWS 'too low terrain' warning sounded. Vertical speed was near zero with the altitude at about 900 ft. The captain applied additional pitch up and simultaneously the tower cleared us to climb to 3000 ft. Before that altitude could be set and acknowledged the aircraft was climbing so rapidly that we went above 4000 ft. The tower told us to contact departure control and reiterated that we were to maintain 3000 ft. By this time the overshoot was evident and power and pitch angle were reduced to return to 3000 ft. It is my recollection that a right turn was commenced at the time of pull up and we should have remained over the airport and well west of the river's east bank. The 'too low terrain' warning is therefore a complete mystery to me. With toga power set and a pitch attitude of at least 10 degrees it seems incongruous that we were not already climbing rapidly and well above 900 ft. We were in heavy rain as we executed the missed approach and even though we had no 'wind shear' alert, no turbulence, perhaps we were caught in a strong downdraft or vertical shear that caused the aircraft to cease climbing for a brief period. But that does not explain the 'too low terrain' either. Clearly the additional pitch applied at the onset of the 'too low terrain' warning was excessive for normal circumstances but with the urgency of the moment it was the only appropriate action. It is my opinion that with that much thrust and that much pitch that it would have been very difficult to stop the climb at 3000 ft under a more normal circumstance. After approximately 12-15 mins we were vectored for the 36 ILS and landed in basically VFR conditions with rainshowers still scattered in the vicinity.

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Original NASA ASRS Text

Title: LGT HAS GPWS ACTIVATE DURING MAP, THEN CLBS ABOVE ASSIGNED ALT.

Narrative: WE WERE CONDUCTING THE LDA-DME APCH TO RWY 18 AT DCA IN VARIABLE IFR CONDITIONS, WITH RAINSHOWERS IN THE VICINITY AND WITH THE POTOMAC RIVER IN SIGHT AS WE PASSED BELOW ABOUT 1500 FT MSL. BY THAT TIME WE WERE IN LNDG CONFIGN WITH ALL CHKLISTS AND SOP'S ACCOMPLISHED AND THE MISSED APCH ALT 1800 FT SET IN THE ALT REMINDER. AT ABOUT 1200 FT MSL THE CAPT DISCONNECTED THE AUTOPLT, AS WE WERE IN WHAT APPEARED TO BE IMPROVED CONDITIONS BELOW THE MAJORITY OF THE CLOUDS, AND WE CONTINUED TOWARD THE 720 FT MSL MDA ON LOC AND GS. AT ABOUT 1000 FT THE TWR CTLR ADVISED THAT A HVY RAINSHOWER HAD JUST MOVED OVER THE FIELD AND ASKED IF WE COULD SEE THE ARPT. I ADVISED THAT WE COULD NOT. AT THE MDA THE CAPT INITIATED THE MISSED APCH WITH TOGA THRUST AND A PITCH UP. WING FLAPS WERE CALLED FOR POS 1 AND I SELECTED POS 1 AND THEN WITH A POSITIVE RATE OF CLB THE GEAR WAS CALLED UP, WHICH I THEN SELECTED UP. I ADVISED THE TWR THAT WE HAD MISSED TO WHICH THE TWR INSTRUCTED US TO FLY THE 185 RADIAL (PUBLISHED MISS-DCA 185). WITHIN SECONDS THE GPWS 'TOO LOW TERRAIN' WARNING SOUNDED. VERT SPD WAS NEAR ZERO WITH THE ALT AT ABOUT 900 FT. THE CAPT APPLIED ADDITIONAL PITCH UP AND SIMULTANEOUSLY THE TWR CLRED US TO CLB TO 3000 FT. BEFORE THAT ALT COULD BE SET AND ACKNOWLEDGED THE ACFT WAS CLBING SO RAPIDLY THAT WE WENT ABOVE 4000 FT. THE TWR TOLD US TO CONTACT DEP CTL AND REITERATED THAT WE WERE TO MAINTAIN 3000 FT. BY THIS TIME THE OVERSHOOT WAS EVIDENT AND PWR AND PITCH ANGLE WERE REDUCED TO RETURN TO 3000 FT. IT IS MY RECOLLECTION THAT A R TURN WAS COMMENCED AT THE TIME OF PULL UP AND WE SHOULD HAVE REMAINED OVER THE ARPT AND WELL W OF THE RIVER'S E BANK. THE 'TOO LOW TERRAIN' WARNING IS THEREFORE A COMPLETE MYSTERY TO ME. WITH TOGA PWR SET AND A PITCH ATTITUDE OF AT LEAST 10 DEGS IT SEEMS INCONGRUOUS THAT WE WERE NOT ALREADY CLBING RAPIDLY AND WELL ABOVE 900 FT. WE WERE IN HVY RAIN AS WE EXECUTED THE MISSED APCH AND EVEN THOUGH WE HAD NO 'WIND SHEAR' ALERT, NO TURB, PERHAPS WE WERE CAUGHT IN A STRONG DOWNDRAFT OR VERT SHEAR THAT CAUSED THE ACFT TO CEASE CLBING FOR A BRIEF PERIOD. BUT THAT DOES NOT EXPLAIN THE 'TOO LOW TERRAIN' EITHER. CLRLY THE ADDITIONAL PITCH APPLIED AT THE ONSET OF THE 'TOO LOW TERRAIN' WARNING WAS EXCESSIVE FOR NORMAL CIRCUMSTANCES BUT WITH THE URGENCY OF THE MOMENT IT WAS THE ONLY APPROPRIATE ACTION. IT IS MY OPINION THAT WITH THAT MUCH THRUST AND THAT MUCH PITCH THAT IT WOULD HAVE BEEN VERY DIFFICULT TO STOP THE CLB AT 3000 FT UNDER A MORE NORMAL CIRCUMSTANCE. AFTER APPROX 12-15 MINS WE WERE VECTORED FOR THE 36 ILS AND LANDED IN BASICALLY VFR CONDITIONS WITH RAINSHOWERS STILL SCATTERED IN THE VICINITY.

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.