Air taxi flight crew reported flying into an embedded thunderstorm during cruise. The aircraft encountered severe turbulence and there was a period of loss of control. No aircraft damage or injuries were reported.
Synopsis
Air taxi flight crew reported flying into an embedded thunderstorm during cruise. The aircraft encountered severe turbulence and there was a period of loss of control. No aircraft damage or injuries were reported.
Narrative
On Day; at approximately XA:30; Call Sign X; a Gulfstream G-V encountered embedded thunderstorm activity at FL430 which resulted in a deviation from course and significant loss of altitude. The flight was scheduled from ZZZ to ZZZZ.While in non radar environment of the ZZZ Oceanic airspace; the Gulfstream was in level cruise at FL430 when it entered high level alto cirrus clouds; resulting in an IMC condition. The weather radar was pulled up and was being used to determine any significant weather ahead that could be problematic. As the aircraft briefly transitioned from IMC to VMC; the Captain saw a large building cloud at the aircraft's 12 o clock position; which was not being displayed on the cockpit radar. The crew and passengers were seated and belted as soon as possible; and as the aircraft approached moments later; the speed increased; despite the Captain taking the corrective action of slowing to turbulence penetration speed beforehand. As the aircraft entered the cloud; the resulting windshear and downdrafts forced the plane into a nose down and left hand bank attitude. Over the course of a minute the plane descended from 43;000 feet to 38;500; as the Captain held the wings in a level position and applied full power. Despite the power setting the plane continued to slow and was only holding altitude but not able to climb.After a few minutes the aircraft exited the thunderstorm environment; and eventually gained airspeed and began climbing. A request was made via CPDLC to maintain block 410 to 450 and it was immediately granted. A second message was also sent confirming the severe turbulence and windshear; as well as the safety of the aircraft and those on board. The flight continued without incident to ZZZZ.
Second reporter narrative
On Day; Call Sign X; a Gulfstream GV took off from ZZZ enroute to ZZZZ. The aircraft carried a total of 12 souls (9 passengers; plus 3 crew). The aircraft was under the command of Captain and was assisted by First Officer. While cruising at FL430/.82. at approximately XA26z; the aircraft entered an embedded thunderstorm causing the aircraft to gain about 1;000 ft; followed by a loss of altitude of about 3;5000 ft. The crew had the radar up and running and were painting any possible weather up ahead. At the time; nothing was painting as all the weather was well below FL430. During the preflight phase; there was a SIGMET that was west of the flight path showing tops around FL380. Also; there were multiple cells starting to develop west of the intended flight path. The crew reviewed the weather and had decided to climb as soon as possible to FL430 to avoid any deviations. Upon departure the crew began to ask for deviations left/right of course to avoid build ups. Upon reaching FL430 as planned; all the weather was below. Minutes later; ATC issued an update on a SIGMET and was received via CPDLC. The crew plotted the new coordinates of the SIGMET and it placed the aircraft in the middle of the new issued SIGMET. The weather was well below FL430. As the flight continued; the crew noticed alto cirrus/high level clouds approximately 50-100 miles ahead. The crew began to paint any possible weather on radar. Unfortunately; the crew was unable to climb to a higher altitude as the aircraft was too heavy at the time. The crew did not visually see any build up ahead. But visibility did begin to deteriorate. The crew continued to heavily monitor its radar and again; nothing painted. A few minutes after; the alto cirrus/high level clouds cleared out and the Captain noticed a cell right in front with tops approximate FL450. The Captain was able to turn on the seat belt sign and have all pax and cabin attendant secured. The Captain immediately reduced the aircraft's speed to .80 (Turbulence Penetration Speed). As the aircraft entered the cell; the speed continued to increase to about .85. The Captain fully reduced the power to idle to maintain .80 or less. The aircraft gained approximately 500 ft; followed by a left descending turn causing the aircraft to descend to 38;500. The Captain briefed the first officer that the best thing to do was maintain wings level and attitude. The Captain was able to break the left descending turn at about 38;500 ft. The Captain told the first officer to advice ATC of the situation and to request a block altitude of FL410-FL450. The aircraft struggled a bit to climb and maintain speed. Within 4 minutes of having entered the thunderstorm; the aircraft was able to get back up to FL430 at normal cruising speed of .82. The aircraft did not suffer any damage and or nobody was hurt. All possible pireps were given to ATC via CPDLC.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.