Overview
On November 5, 2009, Air Canada Flight 795 (ACA795) departed Toronto's Lester B. Pearson International Airport at approximately 2010 eastern standard time (0010 UTC November 6) on a non-stop flight to Los Angeles International Airport. The aircraft, whose type and registration are not specified in the source, was cruising at flight level 360 when it checked in with Denver Air Route Traffic Control Center (ZDV) at 2115 Mountain Standard Time. The aircraft's radios were configured with COMM1 on the ATC frequency and COMM2 on 121.5 MHz.
Timeline of Events
At 2134, ZDV radar sector 37 directed ACA795 to contact ZDV on frequency 132.87. ACA795 did not respond. Over the next 37 minutes, multiple attempts were made by ZDV controllers to reestablish communication. This included radio checks on various frequencies, requests to other aircraft (Frontier flights 860, 778, 780, 266, and Continental flight 752) to attempt air-to-air communication, and the use of ACARS messages via Air Canada dispatch. An initial ACARS message from dispatch failed because the airborne ACARS set was on a frequency not available at the New Mexico ground station, and the system did not notify dispatch of the failure for 30 minutes (subsequently changed to 8 minutes).
At 2157, ACA795 used ACARS to obtain LAX weather and ATIS from the San Francisco ARINC server, but this did not reestablish the ACARS link with dispatch. At 2211, ZDV requested N613WF to transmit to ACA795 to contact ZLA. ACA795 received the transmission, and at 2212 N613WF reported establishing communications. N613WF advised ACA795 that ATC had been trying to reach them for 45 minutes. At 2214, ZLA was informed that ACA795 reported being on frequency 125.67 during the NORDO period.
At 2227, ACA795 began its descent into LAX, triggering automatic ACARS reporting that reestablished the link with dispatch. Communication with ZDV was reestablished via air-to-air relay through N613WF at FL490, and ACA795 was directed to contact Los Angeles ARTCC on 127.35.
Aftermath
According to the FAA preliminary pilot deviation report, after landing, the pilot of ACA795 contacted the ZDV Operations Manager-in-Charge and explained that they were receiving static on frequency 121.5 and had turned the volume down. The pilot also stated that they had received ACARS messages after contacting ZLA. Notably, the aircraft's VHF SELCAL notification lacked an audio feature, and the aircraft did not have HF SELCAL.