In-flight encounter with en route WX near thunderstorm activity creates an altitude deviation altitu...

Attributes
ACN	204062
Time
Date	199203
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : sln
State Reference	KS
Altitude	msl bound lower : 6200 msl bound upper : 7000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Operator	common carrier : air taxi
Make Model Name	Small Transport
Flight Phase	cruise other
Route In Use	enroute airway : v244
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : cfi pilot : commercial
Experience	flight time last 90 days : 120 flight time total : 1700 flight time type : 300
ASRS Report	204062
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : returned to intended course or assigned course none taken : unable
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

Departed hys airport en route to sln airport. Level flight at 7000 ft MSL. Nighttime (pm local). Visibility was 25 mi or better, scattered layer of clouds below, estimate tops 5000 ft and bases 4000 ft MSL. Areas of widely scattered thunderstorms in all directions (north/south/east/west), no storms along route of flight, estimate closest thunderstorm was 50+ mi away. Between hys and sln encountered area of moderate turbulence (occasional light turbulence prior to moderate) and noticed small rainshower directly along route of flight. I was going to request a lower altitude or deviate around when I encountered very heavy rain and severe turbulence and strong downdrafts. Aircraft was unable to maintenance altitude due to the strength of the downdraft and lost approximately 800 ft (7000 ft MSL to 6200 ft). At 6200 ft downdraft stopped and airplane climbed normally back to 7000 ft. No further downdrafts and turbulence moderate balance of flight. There was no way to prevent the altitude loss. Velocity of the downdraft greatly exceeded the ability of the aircraft to climb. Only action possible was to climb at vy and maximum continuous power, and ride the downdraft out until airplane flew out the bottom or side of the area of high sink. At night there was no way to see the rainshower, since the storm did not have any lightning in it (it was not a thunderstorm). Airplane was not equipped with WX radar. Prior to entering shower, forward visibility was good, although rain was heavy when downdraft was encountered, it did not block visibility until actually flown into.

Original NASA ASRS Text

Title: INFLT ENCOUNTER WITH ENRTE WX NEAR TSTM ACTIVITY CREATES AN ALTDEV ALT EXCURSION WHEN LOSS OF ACFT CTL OCCURS.

Narrative: DEPARTED HYS ARPT ENRTE TO SLN ARPT. LEVEL FLT AT 7000 FT MSL. NIGHTTIME (PM LCL). VISIBILITY WAS 25 MI OR BETTER, SCATTERED LAYER OF CLOUDS BELOW, ESTIMATE TOPS 5000 FT AND BASES 4000 FT MSL. AREAS OF WIDELY SCATTERED TSTMS IN ALL DIRECTIONS (N/S/E/W), NO STORMS ALONG RTE OF FLT, ESTIMATE CLOSEST TSTM WAS 50+ MI AWAY. BTWN HYS AND SLN ENCOUNTERED AREA OF MODERATE TURB (OCCASIONAL LIGHT TURB PRIOR TO MODERATE) AND NOTICED SMALL RAINSHOWER DIRECTLY ALONG RTE OF FLT. I WAS GOING TO REQUEST A LOWER ALT OR DEVIATE AROUND WHEN I ENCOUNTERED VERY HVY RAIN AND SEVERE TURB AND STRONG DOWNDRAFTS. ACFT WAS UNABLE TO MAINT ALT DUE TO THE STRENGTH OF THE DOWNDRAFT AND LOST APPROX 800 FT (7000 FT MSL TO 6200 FT). AT 6200 FT DOWNDRAFT STOPPED AND AIRPLANE CLBED NORMALLY BACK TO 7000 FT. NO FURTHER DOWNDRAFTS AND TURB MODERATE BAL OF FLT. THERE WAS NO WAY TO PREVENT THE ALT LOSS. VELOCITY OF THE DOWNDRAFT GREATLY EXCEEDED THE ABILITY OF THE ACFT TO CLB. ONLY ACTION POSSIBLE WAS TO CLB AT VY AND MAX CONTINUOUS PWR, AND RIDE THE DOWNDRAFT OUT UNTIL AIRPLANE FLEW OUT THE BOTTOM OR SIDE OF THE AREA OF HIGH SINK. AT NIGHT THERE WAS NO WAY TO SEE THE RAINSHOWER, SINCE THE STORM DID NOT HAVE ANY LIGHTNING IN IT (IT WAS NOT A TSTM). AIRPLANE WAS NOT EQUIPPED WITH WX RADAR. PRIOR TO ENTERING SHOWER, FORWARD VISIBILITY WAS GOOD, ALTHOUGH RAIN WAS HVY WHEN DOWNDRAFT WAS ENCOUNTERED, IT DID NOT BLOCK VISIBILITY UNTIL ACTUALLY FLOWN INTO.

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.

In-flight encounter with en route WX near thunderstorm activity creates an altitude deviation altitude excursion when loss of aircraft control occurs.