Narrative:

I was on a training flight with a friend (instrument, commercial, and CFI ratings) in order to do some night flying and instrument approach practice. We departed boulder, co, near dusk. Solid VFR WX, then flew a couple of approachs at fnl, then after a VOR approach at gxy, landed at gxy for a break and fuel stop. While fueling at gxy, we noticed that calm winds were changing to blustery winds out of the west. Lightning was visible to the northwest, but stars and moon could still be seen in all other quadrants. On initial taxi, AWOS indicated a moderate west wind (approximately 15 KT), but this changed to calm as we arrived at the run-up area for runway 27. Lightning appeared closer, but hard to judge distance. Winds still calm after run-up completed, we took off on runway 27, anticipating a quick retreat to 1v5. Initially, we had a good rate of climb (400-500 FPM) until I turned south and away from the lightning, still to our northwest at approximately 500-600 ft AGL. At this point, we probably went through a shear layer, as the calm wind had obviously changed - ground track indicated a strong wind from the northwest, and the climb rate diminished to zero, even with the plane pitched for vy. Concerned about possible strong downdrafts (at low altitude), I turned to the west, which provided some minimal climb, on and off, but was problematic as the lightning was now appearing quite close. I then turned south, towards clear skies, still showing poor climb rate -- effectively trying to 'outrun' the approaching thunderstorm. This course took us directly towards the denver class B airspace. Moderate turbulence, nearby lightning, and the difficulties with climb rate, all conspired to make us very concerned with obtaining sufficient altitude. As soon as we encountered updrafts, I pushed us up to nearly 9000 ft MSL. Recognizing that this would bring us above the floor of class B airspace, I asked my friend to get me the denver approach frequency as soon as possible. After some map-fumbling, we got the frequency and called approach -- now just within the boundaries of class B(2-3 NM inside?). We were given a squawk code, and after radar contact we were also given an admonishment for having entered class B airspace without a clearance. I explained that we were intent on avoiding the uncomfortably close thunderstorm activity and we were given a clearance and routing, direct to bjc, at 10500 ft MSL. After listening to the 1v5 AWOS for the bulk of our route, noting strong but steady west winds at approximately 20 KTS, and prior to entering class D airspace, we requested a change in our routing, to 1v5, and arrived uneventfully. Analysis: with limited night flying experience (my friend's total hours are approximately 370 hours), and with no instrumentation for determining lightning distance, we mistakenly took off into an approaching thunderstorm. Concerns with storm proximity, turbulence, and gaining sufficient altitude caused us to enter class B airspace without a clearance.

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Original NASA ASRS Text

Title: C150 PLT AND SAFETY PLT ENCOUNTER TURB, DOWNDRAFTS, WINDSHEAR AND TSTMS AT NIGHT AND ENTER DEN CLASS B AIRSPACE WITHOUT CLRNC.

Narrative: I WAS ON A TRAINING FLT WITH A FRIEND (INST, COMMERCIAL, AND CFI RATINGS) IN ORDER TO DO SOME NIGHT FLYING AND INST APCH PRACTICE. WE DEPARTED BOULDER, CO, NEAR DUSK. SOLID VFR WX, THEN FLEW A COUPLE OF APCHS AT FNL, THEN AFTER A VOR APCH AT GXY, LANDED AT GXY FOR A BREAK AND FUEL STOP. WHILE FUELING AT GXY, WE NOTICED THAT CALM WINDS WERE CHANGING TO BLUSTERY WINDS OUT OF THE W. LIGHTNING WAS VISIBLE TO THE NW, BUT STARS AND MOON COULD STILL BE SEEN IN ALL OTHER QUADRANTS. ON INITIAL TAXI, AWOS INDICATED A MODERATE W WIND (APPROX 15 KT), BUT THIS CHANGED TO CALM AS WE ARRIVED AT THE RUN-UP AREA FOR RWY 27. LIGHTNING APPEARED CLOSER, BUT HARD TO JUDGE DISTANCE. WINDS STILL CALM AFTER RUN-UP COMPLETED, WE TOOK OFF ON RWY 27, ANTICIPATING A QUICK RETREAT TO 1V5. INITIALLY, WE HAD A GOOD RATE OF CLB (400-500 FPM) UNTIL I TURNED S AND AWAY FROM THE LIGHTNING, STILL TO OUR NW AT APPROX 500-600 FT AGL. AT THIS POINT, WE PROBABLY WENT THROUGH A SHEAR LAYER, AS THE CALM WIND HAD OBVIOUSLY CHANGED - GND TRACK INDICATED A STRONG WIND FROM THE NW, AND THE CLB RATE DIMINISHED TO ZERO, EVEN WITH THE PLANE PITCHED FOR VY. CONCERNED ABOUT POSSIBLE STRONG DOWNDRAFTS (AT LOW ALT), I TURNED TO THE W, WHICH PROVIDED SOME MINIMAL CLB, ON AND OFF, BUT WAS PROBLEMATIC AS THE LIGHTNING WAS NOW APPEARING QUITE CLOSE. I THEN TURNED S, TOWARDS CLR SKIES, STILL SHOWING POOR CLB RATE -- EFFECTIVELY TRYING TO 'OUTRUN' THE APCHING TSTM. THIS COURSE TOOK US DIRECTLY TOWARDS THE DENVER CLASS B AIRSPACE. MODERATE TURB, NEARBY LIGHTNING, AND THE DIFFICULTIES WITH CLB RATE, ALL CONSPIRED TO MAKE US VERY CONCERNED WITH OBTAINING SUFFICIENT ALT. AS SOON AS WE ENCOUNTERED UPDRAFTS, I PUSHED US UP TO NEARLY 9000 FT MSL. RECOGNIZING THAT THIS WOULD BRING US ABOVE THE FLOOR OF CLASS B AIRSPACE, I ASKED MY FRIEND TO GET ME THE DENVER APCH FREQ ASAP. AFTER SOME MAP-FUMBLING, WE GOT THE FREQ AND CALLED APCH -- NOW JUST WITHIN THE BOUNDARIES OF CLASS B(2-3 NM INSIDE?). WE WERE GIVEN A SQUAWK CODE, AND AFTER RADAR CONTACT WE WERE ALSO GIVEN AN ADMONISHMENT FOR HAVING ENTERED CLASS B AIRSPACE WITHOUT A CLRNC. I EXPLAINED THAT WE WERE INTENT ON AVOIDING THE UNCOMFORTABLY CLOSE TSTM ACTIVITY AND WE WERE GIVEN A CLRNC AND ROUTING, DIRECT TO BJC, AT 10500 FT MSL. AFTER LISTENING TO THE 1V5 AWOS FOR THE BULK OF OUR RTE, NOTING STRONG BUT STEADY W WINDS AT APPROX 20 KTS, AND PRIOR TO ENTERING CLASS D AIRSPACE, WE REQUESTED A CHANGE IN OUR ROUTING, TO 1V5, AND ARRIVED UNEVENTFULLY. ANALYSIS: WITH LIMITED NIGHT FLYING EXPERIENCE (MY FRIEND'S TOTAL HRS ARE APPROX 370 HRS), AND WITH NO INSTRUMENTATION FOR DETERMINING LIGHTNING DISTANCE, WE MISTAKENLY TOOK OFF INTO AN APCHING TSTM. CONCERNS WITH STORM PROX, TURB, AND GAINING SUFFICIENT ALT CAUSED US TO ENTER CLASS B AIRSPACE WITHOUT A CLRNC.

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.