Authorities investigating the deadly crash of a Cessna Citation S550 in San Diego on Thursday are looking at the possibility that a lack of current weather, specifically an altimeter setting at the destination airport, may have contributed to the accident.
There was heavy fog and low visibility in the area at the time of the crash. The pilot was attempting to fly the RNAV GPS approach to Runway 28R at Montgomery-Gibbs Executive Airport (KMYF).
ADS-B data of the jet’s path show it had descended below the published glideslope. It collided with high-voltage powerlines approximately 2 miles southeast of the airport. National Transportation Safety Board (NTSB) officials reported finding parts of the jet beneath the power lines.
According to the FAA, the pilot and all five passengers on board were killed when the Citation came down in a densely packed neighborhood at 3:46 a.m. PDT, resulting in a massive fire that heavily damaged at least 15 homes and destroyed multiple cars in the neighborhood described as military housing.
One-hundred people were evacuated from their homes, and there were reports of at least eight people injured on the ground from smoke inhalation and exposure to burning jet fuel. Photographs and video from the scene show burned-out homes and cars, and jet wreckage strewn in streets and yards.
History of the Flight
According to preliminary information gleaned from ADS-B data as published on FlightAware.com, the jet departed from Teterboro Airport (KTEB) in New Jersey at approximately 11:15 p.m. EDT on Thursday. The jet flew for 3.5 hours to Colonel James Jabara Airport (KAAO) in Wichita, Kansas, where it was refueled. At 2:36 a.m. CDT, it departed on the last leg of the flight to San Diego.
LiveATC.com recordings of conversations between the pilot of the jet and local air traffic control (ATC) contain discussions of the weather at Montgomery-Gibbs Executive Airport. It was noted that the automated surface observation system (ASOS) at the airport was out of service. The pilot asked about the weather conditions, specifically visibility at other nearby airports.
Normally, when a pilot obtains the weather from the ASOS, it includes visibility, sky condition, and altimeter. A lack of a correct altimeter setting can cause a pilot to fly at the wrong altitude.
According to chapter 7, meteorology in the FAA’s Aeronautical Information Manual, if the altimeter setting is higher than actual conditions, it can introduce an error of 100 feet for every 0.1 inches of mercury the setting is off. Pilots are taught “from high (pressure) to low (lower pressure) lookout below, you will be flying lower than the (incorrectly set) altitude indicates).”
The weather at the time of the accident included an AIRMET active for IFR conditions with ceilings below 1,000 feet and visibility less than 3 miles due to fog and mist.
The controller gave the weather for San Diego’s Marine Corps Air Station Miramar (KNKX) 3 miles to north, which was reporting visibility of one-half mile, and the pilot mentioned having checked the weather at Gillespie Field (KSEE) in El Cajon, California, 8 nm to the east. But he added that he was aware that the weather at KMYF could be different, and he had checked the weather at Brown Field Municipal Airport (KSDM), which was 17 nm away, but decided against it because the weather minimums for approach were higher.
The controller asked the pilot what he wanted to do, and the pilot requested the RNAV 28R at KMYF. The pilot requested the RNAV GPS 28R at KMYF. According to the published approach procedure, the visibility minimum for the approach is three-quarters of a mile.
The majority of the cross-country flight was done above 18,000 feet, and FAA procedures call for pilots to set their altimeters to 29.92 as they fly at flight levels. Below that altitude, local altimeter settings are used.
The recordings did not contain ATC giving the pilot an altimeter setting, which is normal procedure when a pilot checks with controllers.
Also, the control tower at KMYF was closed at the time of the accident. If the tower had been manned at the time, the controller would have been able to supply the pilot with an altimeter setting and low altitude alert.
The pilot was cleared to fly the RNAV 28R approach and crossed NESTY at 3,600 feet, then PENYY at 2,500, which is the published approach. However, ADS-B data shows the airplane descending below the published glideslope. The approach plate shows the power line towers (the inverted V with a dot in the center in the photograph) at 544 feet along with another tower located slightly to the west at the same elevation. The power lines run across the extended centerline on the aircraft’s approach path to the runway.
More information will be available when the NTSB releases its preliminary report in a few weeks.
