Date:	Friday 9 September 2022
Time:	13:14 LT
Type:	Learjet 36
Owner/operator:	Strategic Airborne Operations
Registration:	N26FN
MSN:	011
Year of manufacture:	1975
Total airframe hrs:	17024 hours
Engine model:	GARRETT TFE-731-2-2B
Fatalities:	Fatalities: 0 / Occupants: 2
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	San Diego-North Island NAS, CA (NZY) -   United States of America
Phase:	Landing
Nature:	Military
Departure airport:	San Diego-North Island NAS, CA (NZY/KNZY)
Destination airport:	San Diego-North Island NAS, CA (NZY/KNZY)
Investigating agency:	NTSB

Narrative:
A Learjet 36, N26FN, callsign FST26, sustained substantial damage after a runway excursion during the landing sequence to runway 36 (8000 feet long) at North Island NAS-Halsey Field (KNZY), San Diego, California. The two pilots onboard sustained minor injuries.

The aircraft was likely operated by Aery Aviation on an electronic warfare exercise mission on behalf of the U.S. Navy. It had taken off at 12:22 and landed back at North Island NAS about 13:14.

The flight crew was supporting a United States Navy (USN) training mission and ended the flight early due to icing conditions. The flight crew calculated a landing reference speed (Vref) of 140 knots (kts) indicated airspeed (KIAS) and landing distance required of 4,200 ft for a wet runway and a flap setting of 20°. Due to underwing-mounted external storage, the landing flaps were limited to a maximum extension of 20°. The flight crew configured the airplane with 20° flaps and reported that the airplane touched down at 140 kts. Although the runway was 8,001 ft long, an arresting cable was located 1,701 ft from the runway threshold, resulting in a runway distance available of about 6,300 ft.
After landing, the second in command (SIC) reported that the pilot-in-command (PIC) deployed the spoilers and brakes, then announced that the airplane was not slowing down. The PIC stated that the airplane did not decelerate normally, that the brake anti-skid system was active, and that the airplane seemed to be hydroplaning. He cycled the brakes, which had no effect. The airplane subsequently overran the departure end of the runway, breached an ocean sea wall and came to rest in a nose-down attitude on a sandbar.
The airport weather observation system recorded that 0.06 inches of liquid equivalent precipitation fell between 18 and 9 minutes before the accident. In the 4 hours before the accident, the airport received 0.31 inches of liquid equivalent precipitation.
A landing performance study conducted by the airplane manufacturer modeled a variety of landing scenarios considered during the investigation. The modeling used factual information provided by the investigation, including ADS-B data, as well as manufacturer-provided airplane performance data specific to the airplane. The study considered the effect on landing distance of both a wet and dry runway, a contaminated runway, both full and intermittent hydroplaning, a localized tailwind (which was not present in the weather data), and an inboard brake failure. The study showed that the most likely scenario, based on the available data, was that the airplane touched down with a ground speed well in excess of the 140 kts Vref speed reported by the crew, and that subsequent to the touchdown encountered full hydroplaning at speeds above 104 kts.
The airplane sat overnight on the sandbar and was submerged in saltwater before the airplane was recovered. As a result, the airplane's braking system could not be functionally tested. However, the physical evidence from the brakes as found postaccident, combined with the results of the landing distance modeling, did not indicate that a brake failure occurred. Similarly, ADS-B data did not support the presence of a localized tailwind when such a landing was modeled in the study. Thus, it's likely that the flight crew landed too fast and then encountered hydroplaning during the landing roll as a result of a recent heavy rain shower, which diminished the calculated stopping distance.

Probable Cause: The flight crew's fast landing on a wet runway, which resulted in the airplane hydroplaning during the landing roll and subsequently overrunning the runway.

19:52 UTC / 12:52 local time:
KNZY 091952Z 00000KT 3SM +RA BR BKN035 BKN045 OVC060 24/23 A2952 RMK AO2 SLP995 P0008 T02440228

20:05 UTC / 13:05 local time:
KNZY 092005Z 20006KT 2 1/2SM +RA BR BKN033 BKN045 OVC055 25/23 A2951 RMK AO2 P0006 T02500228

20:52 UTC / 13:52 local time:
KNZY 092052Z 24007KT 6SM -RA BR FEW020 SCT040 OVC070 24/23 A2953 RMK AO2 SLP998 P0012 60029 T02440228 51007

NTSB WPR22LA344

Other occurrences involving this aircraft


1 December 2006

N26FN

L-3 Communications Flight Internata

0

San Diego, California

sub

Date/time	Contributor	Updates
27-Oct-2024 20:58	ASN Update Bot	Updated [Time, Cn, Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative, Category, Accident report, ]
27-Oct-2024 21:04	ASN	Updated [Other fatalities, Nature, Departure airport, Destination airport, Narrative, ]