ASN Wikibase Occurrence # 229481
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| Date: | Thursday 14 June 2018 |
| Time: | 20:26 LT |
| Type: |  Bombardier DHC-8-402Q Dash 8 |
| Owner/operator: | Ryukyu Air Commuter |
| Registration: | JA84RC |
| MSN: | 4550 |
| Fatalities: | Fatalities: 0 / Occupants: |
| Aircraft damage: | None |
| Location: | Okinawa-Naha Airport (OKA/ROAH) -
 Japan
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | |
| Okinawa-Naha Airport (OKA/ROAH) | |
| Investigating agency: | JTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
At Naha Air Base in Japan two aircraft were deployed at the scramble-ready hangar to stand ready to scramble against intrusions into territorial airspace
On the day of the serious incident, it was raining intermittently from the morning repeating instrument meteorological conditions (IMC) and visual meteorological conditions (VMC) at Naha airport with rain front accompanying low pressure in the vicinity of main island of Okinawa. Therefore, both the lead aircraft (F-15J, registered 52-8850) and the no. 2 aircraft (F-15J, registered 32-8818) were scramble-ready equipped with three external tanks fully filled with fuel considering the possibility of being forced to return to an air base located far away.
On that day at around 20:20, a scramble alarm sounded in the alert-standby room. The formation leader and the wingman hopped into their aircraft and taxied out from the Alert Hangar to the apron after having confirmed that there existed no functional anomaly in mutual communications using the radio frequency for use among the formation aircraft. The formation leader presumed, through the visual recognition of the civil aircraft taking off and the light of the a DHC-8-400 (JA84RC), which was visually measured about 10 nm from touchdown on the final approach course, that "smooth take-off was feasible to conduct between those two aircraft".
At around 20:23, the formation leader established radiocommunication with the Naha Ground on the frequency for ATC use. The Naha Ground controller instructed the formation aircraft to taxi to E7 taxiway, and simultaneously gave them the flight direction, the frequency to be contacted, and other post-take-off instructions. The wingman confirmed the communications between the Naha Ground and the formation leader.
The lead aircraft commenced taxiing to E7 taxiway followed by the no. 2 Aircraft. The formation leader was perplexed by the taxiway centerline lights which were not installed along his taxi route from A7 to E7, because, in addition to the night time operation, this was his first time to taxi from the the Alert Hangar of the Naha Air Base. Besides, the wingman could not timely adapt to the darkness immediately after getting out of the well-lighted Alert Hangar; therefore he was taxiing attentively confirming the position of the lead aircraft and the taxiway edge lights, which slightly delayed the move of the no. 2 aircraft after the lead aircraft.
The formation leader notified the Naha Tower of "Ready for departure" when it entered near the taxiway E7. The Naha Tower controller decided to have the DHC-8 land first based on the judgement that it would be difficult to maintain the ATC separation if the scramble aircraft took off between the departing civil aircraft and the DHC-8 because the scramble aircraft would shortly catch up with the civil departure aircraft. Accordingly, the Naha Tower issued the instruction of "Hold short of runway 36, traffic on final" to the scramble aircraft by using the frequencies of both UHF band and VHF one at the same time. The Formation Leader read back "hold short, 36". After receipt of the read back from the formation leader to hold short of runway, the Naha Tower issued the landing clearance to the DHC-8 with VHF at 20:25.
The formation leader was in the middle of trying to find a way to hasten the no. 2 Aircraft, which was slightly delaying, in parallel with paying attention to the steering of the aircraft on wet taxiways, which became heavier due to three external tanks fully filled with fuel. The formation leader recognized that the landing light of the DHC-8 he saw just before he had entered the runway was as close as 3 nm by eye measurement. The lead aircraft entered the runway around 20:26 without halting short of the holding position marking on the taxiway. The radiocommunication procedure for aircraft in formation at the Naha Air Base stipulates that the lead aircraft shall enter a runway after confirming the read back of ATC instructions by the last aircraft; however, the formation leader was not aware that he had entered the runway without confirming the read back by the wingman. The wingman wondered why the lead aircraft did not hold short of the runway, but thought that he must have missed the "line up and wait" clearance from the controller; thereafter, he entered the runway following the lead aircraft.
By watching the movement of anti-collision lights of the scramble aircraft, the Naha Tower became aware that they entered the runway without obtaining the clearance; accordingly, immediately thereafter he instructed both aircraft to vacate the runway, and simultaneously he cancelled the landing clearance given to the DHC-8 and instructed it to continue its approach as it was doing so.
The PIC and the first officer of the DHC-8 considered the possibility of go-around, but they did not feel the danger because they were flying as instructed by the controller. On the other hand, the cancellation of the scramble order was notified to the lead aircraft and the no. 2 Aircraft from the alert-standby room around the time when both aircraft entered the runway.
The Naha Tower confirmed that the lead aircraft and the no. 2 aircraft vacated the runway and entered the taxiway E6S, and then, he re-issued landing clearance to the DHC-8 at 20:26. The DHC-8 landed on the runway at 20:27.
PROBABLE CAUSES
In this serious incident, it is highly probable that two scramble aircraft in formation misinterpreted the instruction of the air traffic controller; thus, they entered the runway where the Aircraft A was approaching for landing after obtaining landing clearance.
It is probable that the misinterpretation of the instruction of the air traffic controller by the scramble aircraft was contributed by the fact that the Formation Leader and the Wingman, who were temporarily working at the Naha Air Base, were paying a great deal of attention to their taxiing under time pressure, that they were not familiarized with the environment at Naha airport such as lighting facilities, and so on., and that they had not completely acquired the operations implemented at the Naha Air Base such as radiocommunications, and so on.
Accident investigation:
 |
|
Sources:
JTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 29-Sep-2019 17:27 | harro | Added |
| 29-Sep-2019 17:29 | harro | Updated [Location, Narrative] |
| 29-Sep-2019 17:30 | harro | Updated [Narrative] |
Corrections or additions? ... Edit this accident description
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