Narrative:

There was a 'northeaster' in area covering virginia and maryland. Ceiling 800 ft; moderate rain and turbulence; and it got worse as you descended below 3000 ft. I made another approach 1 hour earlier at miv. Flying in this WX is not unusual for me; and consider myself good to excellent in lndgs with gusty winds of up to 32 KTS; and have done it before in VFR conditions over various parts of the country. The wind was out of the northeast about 22 KTS. As I approached 2000 ft; the controller asked me to keep my speed up due to jets behind me going faster. I did not change power setting which was 31 manifold and 2500 RPM. I told the controller I could maintain 155 KTS and I was doing 170-190 on the ground. I was cleared for the approach but wanted to remain level at 2000 ft over middle marker so I could view the GS moving correctly; to be sure it is working (a check I do on every approach). All of a sudden; I started climbing to 2150 ft very quickly; but my airspeed indicated at 187 KTS; which is 12 KTS below red line. I reduced power and pushed down but was still climbing due to some wind gusts or terrain creating updrafts. No thunderstorms were present; nor were any forecasted. I could not make a report 'unable to maintain altitude' to the controller because he was busy transmitting. I brought the power down more; but not before I hit 2350 ft; 350 ft above my assigned altitude. When the controller finally got to me; he said I hit 2400 ft but I was assigned 2000 ft. TCAS showed no conflict. ATC said 'don't worry' and canceled approach clearance; and I proceeded later with no incident. Could have been avoided if I told controller I needed slower speed for approach.

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Original NASA ASRS Text

Title: PA34 EXPERIENCES ALTDEV IN TURB ON APCH TO IAD.

Narrative: THERE WAS A 'NORTHEASTER' IN AREA COVERING VIRGINIA AND MARYLAND. CEILING 800 FT; MODERATE RAIN AND TURB; AND IT GOT WORSE AS YOU DSNDED BELOW 3000 FT. I MADE ANOTHER APCH 1 HR EARLIER AT MIV. FLYING IN THIS WX IS NOT UNUSUAL FOR ME; AND CONSIDER MYSELF GOOD TO EXCELLENT IN LNDGS WITH GUSTY WINDS OF UP TO 32 KTS; AND HAVE DONE IT BEFORE IN VFR CONDITIONS OVER VARIOUS PARTS OF THE COUNTRY. THE WIND WAS OUT OF THE NE ABOUT 22 KTS. AS I APCHED 2000 FT; THE CTLR ASKED ME TO KEEP MY SPD UP DUE TO JETS BEHIND ME GOING FASTER. I DID NOT CHANGE PWR SETTING WHICH WAS 31 MANIFOLD AND 2500 RPM. I TOLD THE CTLR I COULD MAINTAIN 155 KTS AND I WAS DOING 170-190 ON THE GND. I WAS CLRED FOR THE APCH BUT WANTED TO REMAIN LEVEL AT 2000 FT OVER MIDDLE MARKER SO I COULD VIEW THE GS MOVING CORRECTLY; TO BE SURE IT IS WORKING (A CHK I DO ON EVERY APCH). ALL OF A SUDDEN; I STARTED CLBING TO 2150 FT VERY QUICKLY; BUT MY AIRSPD INDICATED AT 187 KTS; WHICH IS 12 KTS BELOW RED LINE. I REDUCED PWR AND PUSHED DOWN BUT WAS STILL CLBING DUE TO SOME WIND GUSTS OR TERRAIN CREATING UPDRAFTS. NO TSTMS WERE PRESENT; NOR WERE ANY FORECASTED. I COULD NOT MAKE A RPT 'UNABLE TO MAINTAIN ALT' TO THE CTLR BECAUSE HE WAS BUSY XMITTING. I BROUGHT THE PWR DOWN MORE; BUT NOT BEFORE I HIT 2350 FT; 350 FT ABOVE MY ASSIGNED ALT. WHEN THE CTLR FINALLY GOT TO ME; HE SAID I HIT 2400 FT BUT I WAS ASSIGNED 2000 FT. TCAS SHOWED NO CONFLICT. ATC SAID 'DON'T WORRY' AND CANCELED APCH CLRNC; AND I PROCEEDED LATER WITH NO INCIDENT. COULD HAVE BEEN AVOIDED IF I TOLD CTLR I NEEDED SLOWER SPD FOR APCH.

Data retrieved from NASA's ASRS site as of January 2009 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.