Peach A320 at Okinawa on Apr 28th 2014, descended below minimum safe height

Last Update: August 1, 2016 / 15:39:46 GMT/Zulu time

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Photo of Peach Aviation JA802P, Airbus A320 — Peach Aviation JA802P, Airbus A320 (Photo credit: redlegsfan21 / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Apr 28, 2014

Classification
Incident

Airline
Peach Aviation

Flight number
MM-252

Departure
Ishigaki, Japan

Destination
Okinawa, Japan

Aircraft Registration
JA802P

Aircraft Type
Airbus A320

ICAO Type Designator
A320

A Peach Aviation Airbus A320-200, registration JA802P performing flight MM-252 from Ishigaki to Okinawa (Japan) with 53 passengers and 6 crew, was on approach to Okinawa's Naha Airport runway 18 when the aircraft descended prematurely below minimum safe height, the aircraft aborted the approach and went around. The aircraft positioned for another approach and landed safely about 22 minutes after first descending below minimum safe height.

Japan's Ministry of Transport rated the occurrence a serious incident and opened an investigation.

Japan's Transportation Safety Board (JTSB) reported on May 1st 2014, that the ground proximity warning system activated on approach to Naha prompting the go-around. The JTSB is investigating the occurrence rated a serious incident.

On May 6th 2014 the French BEA reported in their weekly bulletin: "During approach to Naha Airport, as EGPWS warning occurred, the flight crew executed an emergency operation to avoid crash into water." The occurrence was rated a serious incident and is being investigated by the JTSB.

The airline confirmed the aircraft descended below the required approach path during final approach to Naha Airport and stated: "Peach Aviation Limited (Peach) extends its sincere apologies for any inconvenience and anxiety caused to customers onboard and parties concerned." The airline fully cooperates with the Ministry of Transport and Japan's Transportation Safety Board (JTSB) investigation the occurrence. 4 flights needed to be cancelled as result of the occurrence.

Radar data show the aircraft descended to 1000 feet MSL about 21nm before touchdown (Minimum Safe Altitude MSA 3000 feet) and continued at 1000 feet across the intermediate approach fix (IF, MSA 2000 feet). The crew subsequently descended to or below minimum descent altitude before initiating a go-around.

On Aug 1st 2016 the JTSB released their final report concluding the probable causes of the serious incident were:

It is highly probable that the serious incident occurred because the Captain executed an emergency operation in order to avoid crash into water as the aircraft, making an approach for RWY 18 by precision approach radar-guidance at Naha Airport, began descent and continued.

It is probable that the aircraft began descent due to the captain's unintentional operation. It is also probable that the aircraft continued descending because the Captain and the First Officer were less aware of monitoring the altitude as they relied on autopilot system over maintaining of altitude and did not properly prioritize their tasks.

In addition, it is probable that insufficient risk management at the Naha Ground Controlled Approach Facility, relating to identification of that aircraft before meeting glide-path might descend and deviate below the Radar Safety Zone, consequently contributed to its continued descent of the Aircraft.

The captain (45, ATPL, 9,353 hours total, 661 hours on type) was pilot flying, the first officer (38, CPL, 4,626 hours total, 1,387 hours on type) was pilot monitoring.

A student controller was operating at Okinawa Tower under supervision of a fully licensed training supervisor. A VOR approach to runway 18 was active and the crew prepared for that approach, the captain, who was aware that preceding aircraft had requested a PAR (Precision Approach Radar) approach due to deteriorating weather, held an extra briefing to prepare for transition to and execution of a PAR approach.

The captain subsequently requested a PAR approach, the approach was granted and the controller instructed the crew to not acknowledge the instructions.

The captain had often performed PAR approaches, he used to preprogram a vertical rate of descent higher than needed to initiate the descent upon controller instruction. For the approach to Okinawa he preset the vertical speed to -900 feet per minute intending to just pull the knob to activate the descent as soon as the controller instructed the descent. The captain pre-selected that vertical speed about 5.7nm from the runway threshold, the descent would begin at 3nm before the runway threshold. The captain did not advise the first officer of his pre-selection.

The aircraft began to descend soon after, before reaching 3nm out. The FDR identified the VS knob had been pulled at 5.7nm out.

The first officer warned the captain, the PAR controller instructed the aircraft to maintain 1000 feet also instructing to read back that instruction, the EGPWS issued a "TOO LOW" and "TERRAIN" warning, the captain initiated a go-around. The lowest radio height was 241 feet.

The aircraft subsequently positioned for another PAR approach and landed safely.

The JTSB analysed: "the VS knob was pulled at the position of about 5.7 nm which had considerable distance from the planned initiating descent point of 3.0 nm; therfore, it is highly probable that the presetting operation of the VS knob was made in advance of pulling operation of the VS knob. With this, it is probable that the Captain at that time preset the vertical speed of - 900 fpm by VS knob without attentively confirming the position of the Aircraft."

The JTSB analysed with respect to "Maintaining Attention":

(1) Situations of the Captain and the First Officer

As described in 3.5.1 (3), it is probable that the Captain at the serious incident had a conscious desire to perform PAR approach accurately and was flying while considering upcoming operations, and after transferred to the Final Controller he had been concentrated on the radar-guidance.

On the other hand, as described in 3.4.4, it is probable that the First Officer at that time was unable to read out the Checklist timely due to continuous ATC instructions and that it took a long time to complete its overall procedures of the Checklist. It is probable that eventually the First Officer paid lots of attention to monitoring the Captain’s operations and completing the Checklist in her mind during this timeframe.

(2) Prioritization of Tasks

The first item of the GOLDEN RULES FOR PILOTS described in 2.12.1 requires for the crewmembers to concentrate on "Fly. Navigate. Communicate." as the highest priority and use appropriate task sharing. "The WG Report in 2013" mentioned in 2.13.2 also emphasizes the importance of task management.

As described in the above (1), it is probable that the Captain and the First Officer prioritized the radar-guidance by the Final Controller and completion of the Checklist over monitoring whether the Aircraft is safely flying with maintaining an altitude. However, it is probable, at this phase before meeting a glide-path, that they should have prioritized the monitoring task for the altitude to fly safely, and that they should have followed the radar-guidance by the Final Controller or attempted to complete the Checklist after remaining vigilant in maintaining the altitude in the same manner as they do when they fly by manual maneuvering. The Company should improve its educational and training programs in order to provide the crewmembers with opportunities, such as at CRM training, to acquire the practice of prioritizing a task in an appropriate way.

The JTSB analysed with respect to the go around:

according to FCOM when a PULL-UP warning was issued, a pilot shall simultaneously perform the following items, disengaging the AP, pulling the side-stick to the maximum pitch-up position and setting the thrust levers to the TOGA position, It is probable that it is because the aircraft to which the PULL-UP warning was issued is close to the ground or water enough to perform a defined emergency operation, and then a pilot shall make aircraft climb in a safe and immediate manner to avoid crash into the ground or water.

As described in 2.1.1, AP of the Aircraft was engaged throughout the serious incident, and as described in 2.14, the Aircraft, deviating and descending from an altitude of 1,000 ft with a vertical speed of - 900 fpm in average, moved into a go-around at the stage of its vertical speeds was declining, which was produced by the Captain's operation of pushing VS knob.

With respect to air traffic control the JTSB analysed, before the low altitude warning activating at the approach controller's desk:

As described in Appended Figure 7, the Final Trainee began to communicate with the Aircraft at 11:46:20, gave the Don't Acknowledge Instruction from 11:46:26 to 11:46:29 and began to provide the Aircraft with radar-guidance. From 11:46:30 to 11:46:31, the Final Trainee informed that the Aircraft had passed the position of 6 nm, and from 11:46:32 to 11:46:38, gave heading instructions concerning directions. As described in 3.4.2, it is probable that the Aircraft began descent at 11:46:33 when the Final Trainee was giving the heading instruction. Afterward, the Final Trainee gave the Aircraft such as wind information, heading instructions to align with the final course with its deviation and a report of its passing 5 nm, while he did not give any instructions regarding its altitude.

As described in 2.20.1, the minimum altitude of the Radar Safety Zone in the part of level-flight before the glide-path-capture point for RWY 18 at the Airport is 750 ft, but according to Table 1, Section 2.14, the Aircraft passed pressure altitude of 746 ft at 11:46:55. Therefore, it is probable that the Aircraft had already deviated from the Radar Safety Zone at this point and continued descending. It is probable, however, that the Final Supervisor and the Final Trainee did not notice that the Aircraft was descending.

After the "Low Altitude" warning activated on the approach controller's desk the JTSB analysed:

As described in Appended Figure 7, at 11:47:09 when the Final Trainee reported a landing clearance to the Aircraft, it is probable that an LA was issued at the Pattern Controller's position and the aural warning also sounded. As described in 2.1.2 (3) and (4), the Final Supervisor and the Final Trainee stated that they heard an LA warning, which means that it is probable that both of them noticed that an LA was issued by aircraft under the control of either the Pattern Controller or the Final Controller. It is probable that the pressure altitude of the Aircraft was 558 ft, as shown in Appended Figure 7, when the LA was issued at the Pattern Controller's position at 11:47:09.

It is probable that the Pattern Controller who controlled the following aircraft of the Aircraft at that time recognized that an LA was issued and confirmed "LA" in its data block of the Aircraft on the ARTS Screen, waited for four seconds to update the data in the screen, as described in 2.19.2 (1), and made sure to identify the LA issuance to it then advised the Final Trainee that the Aircraft was descending.

It is probable that the Final Trainee, who was advised by the Pattern Controller that the Aircraft was descending, confirmed that the Aircraft's altitude was shown lower than usual in the elevation indication and instructed "the Maintain 1,000 ft Call" at 11:47:25. It is probable that the pressure altitude of the Aircraft at that time was 322 ft as shown in Appended Figure 7.

As described in 2.1.2 (3), it is probable that the Final Supervisor instructed the Final Trainee to call again in the same manner to the Aircraft since it did not seem to stop descending even after the Final Trainee's instructing "the Maintain 1,000 ft Call." With this, it is probable that the Final Trainee gave "the Acknowledge Call" from 11:47:33 to 11:47:35 and gave the second instruction of maintaining 1,000 ft from 11:47:37 to 11:47:40.

After that, it is probable that the Final Supervisor and the Final Trainee received a go-around call from the Aircraft at 11:47:41, and then confirmed that it recovered the altitude on the PAR Screen.

Metars:
ROAH 280400Z 17012KT 7000 SHRA FEW005 BKN010 BKN030 23/21 Q1011
ROAH 280330Z 17010KT 5000 -SHRA SCT007 BKN010 23/21 Q1012 RMK 3ST007 6CU010 A2988
ROAH 280304Z 16012KT 5000 -SHRA FEW007 BKN010 BKN040 23/21 Q1012 RMK 2ST007 5CU010 7SC040 A2989
ROAH 280300Z 16012KT 4500 R18/P1800N SHRA FEW007 BKN010 23/21 Q1012
ROAH 280238Z 17014KT 4000 SHRA SCT010 BKN013 FEW020TCU 23/20 Q1012 RMK 4CU010 7CU013 2TCU020 A2989 TCU 8KM N AND 15KM SW MOV E
ROAH 280230Z 17014KT 6000 SHRA SCT010 BKN013 FEW020TCU 23/20 Q1012 RMK 4CU010 7CU013 2TCU020 A2989 TCU 15KM SW AND N MOV E
ROAH 280215Z 16011G21KT 140V200 9000 SHRA SCT010 BKN013 FEW020TCU 23/20 Q1012 RMK 4CU010 7CU013 2TCU020 A2989 4000SW-NW TCU 15KM SW-NW MOV E
ROAH 280200Z 17014KT 9999 -SHRA SCT010 BKN013 FEW020TCU 23/19 Q1012 RMK 4CU010 7CU013 1TCU020 A2990 TCU 20KM SW AND NW MOV E
ROAH 280130Z 16015KT 9999 VCSH FEW010 BKN013 FEW020TCU 24/20 Q1011 RMK 1CU010 6CU013 1TCU020 A2988 TCU 20KM W MOV E
ROAH 280100Z 16015KT 9999 FEW010 BKN013 23/20 Q1012 RMK 1CU010 6CU013 A2989
ROAH 280030Z 15016KT 9999 SCT012 BKN040 23/19 Q1012 RMK 3CU012 6SC040 A2989
ROAH 280000Z 15012KT 9999 -SHRA FEW012 SCT023 BKN038 22/20 Q1011 RMK 1CU012 4CU023 6SC038 A2988

Map and flight trajectory (Graphics: AVH/Google Earth):

Okinawa runway 18 VOR/TACAN Approach Chart (Graphics: AIP Japan):