A lear 45 flight crew experiences high altitude windshear and is unable to maintain airspeed and alt...

Attributes
ACN	570008
Time
Date	200301
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : sju.vortac
State Reference	PR
Altitude	msl bound lower : 4650 msl bound upper : 4800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zsu.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 45
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 25 flight time total : 10100 flight time type : 700
ASRS Report	570008
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other non adherence : clearance other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : regained aircraft control flight crew : exited adverse environment flight crew : took evasive action
Supplementary
Problem Areas	ATC Human Performance Environmental Factor Weather
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

I had climbed to FL470 for wind. The sat was isa -- 10 degrees, mach .70, weight was 19000 pounds per the manual. I requested a FL470-FL490 block to climb and descend back to FL470 to accelerate to cruise. At FL480, a sudden rise in temperature to isa +5 degrees happened, probably due to a front east of florida, causing a warm air influx at altitude. There was nothing in the temperature charts about this. The mach decreased to .68 mach, and the aircraft wouldn't hold altitude. I descended to FL470, and the aircraft would not hold speed. I had no choice except to ask for a descent to FL450. The controller would not give a lower altitude and told me miami would give it to us. I had to descend to keep the speed from decreasing further. The controller finally gave me FL450 after I was at FL465. No problems after that, as the temperature was 15 at -5 at FL450. I have not seen this temperature flux before. But I will pay more attention to fronts and watch the sat more closely.

Original NASA ASRS Text

Title: A LEAR 45 FLC EXPERIENCES HIGH ALT WINDSHEAR AND IS UNABLE TO MAINTAIN AIRSPD AND ALT.

Narrative: I HAD CLBED TO FL470 FOR WIND. THE SAT WAS ISA -- 10 DEGS, MACH .70, WT WAS 19000 LBS PER THE MANUAL. I REQUESTED A FL470-FL490 BLOCK TO CLB AND DSND BACK TO FL470 TO ACCELERATE TO CRUISE. AT FL480, A SUDDEN RISE IN TEMP TO ISA +5 DEGS HAPPENED, PROBABLY DUE TO A FRONT E OF FLORIDA, CAUSING A WARM AIR INFLUX AT ALT. THERE WAS NOTHING IN THE TEMP CHARTS ABOUT THIS. THE MACH DECREASED TO .68 MACH, AND THE ACFT WOULDN'T HOLD ALT. I DSNDED TO FL470, AND THE ACFT WOULD NOT HOLD SPD. I HAD NO CHOICE EXCEPT TO ASK FOR A DSCNT TO FL450. THE CTLR WOULD NOT GIVE A LOWER ALT AND TOLD ME MIAMI WOULD GIVE IT TO US. I HAD TO DSND TO KEEP THE SPD FROM DECREASING FURTHER. THE CTLR FINALLY GAVE ME FL450 AFTER I WAS AT FL465. NO PROBS AFTER THAT, AS THE TEMP WAS 15 AT -5 AT FL450. I HAVE NOT SEEN THIS TEMP FLUX BEFORE. BUT I WILL PAY MORE ATTN TO FRONTS AND WATCH THE SAT MORE CLOSELY.

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.

A lear 45 flight crew experiences high altitude windshear and is unable to maintain airspeed and altitude.