On June 28th 2018, a King Air C90 VT-UPZ took off from Juhu airport in Mumbai, India on a test flight for renewal of the certificate of airworthiness. On a day when the clouds were hanging low and general visibility limited by rain, the ill-fated aircraft met with an accident killing all onboard and a bystander on the ground.
What was the fault of the Crew?
They trusted the system and god almighty. The sinister forces had an overbearing power on this day of culmination. The accident report released recently is superficial and shies away from convincing the reader of the probable cause of the accident. If one digs a little deeper, the web of alleged corruption in Indian aviation lays bare.
The probable cause as per the report
I must thank the investigators for broadening the scope of the investigation and including human factors and other contributory causes, especially the role of the regulator. The one topic that is of interest to all is the probable cause in an accident where the vital input of flight data recorder to corroborate the facts was not available.
The lengthy report list the probable cause as stall caused by lack of situational awareness due to spatial disorientation triggered by deteriorating weather, a transition from ILS to visual flying and unexpected bank owing to differential engine power.
Investigative procedures require for the reasoning to be logical and may lead to the formulation of hypotheses which are then discussed and tested against the evidence. Any hypothesis which is not supported by the evidence should be eliminated; it is then important to clearly state the reasons why a particular hypothesis was rejected. When a hypothesis is not based on fact but is an expression of opinion, this should be clearly indicated.
Somatogravic illusion which is a probable cause of loss of situational awareness as stated in the report in fact leads the pilot to push the nose down, which would prevent a stall. The probable cause as mentioned in the report needs to be substantiated to a greater extent for it to be convincing.
New evidence and probable cause of the stall
Minimum control speed, often referred to as VMC is a speed that is associated with the maintenance of directional control during asymmetric flight. If the pilot flies below this speed, the tail fin and rudder are unable to generate enough lift to prevent the aircraft from yawing. If uncorrected, the yaw causes roll, the nose drops, the aircraft rapidly assumes a spiral descent or even dive, and if the aircraft is at low altitude, it will impact steeply into the ground. This type of accident is not uncommon in a multi-engine aircraft during training or actual engine failure.
Relationship between Bank Angle and VMCA
Bank angle and weight have a great effect on the actual VMCA of a multi-engine airplane. It proves that the VMCA that is presented in the Airplane Flight Manual is valid only if the same bank angle is being maintained that was used to determine VMCA, i.e. during unaccelerated, 1g, constant heading flight and definitely not during turns. Any other bank angle will result in a higher actual VMCA and might lead to control problems if the power setting is high, and the airspeed and weight are as low as used during VMCA testing.
This analysis should be used to improve engine emergency procedures and could be used as well to explain the real cause of many accidents after engine failure
Relationship between Flaps. Landing gear & VMCA
The change in CG when the landing gear is put down may make the rudder more effective due to a longer moment arm, which would result in a slighter lower Vmc. The extended gear may also have a tendency to align with the oncoming relative wind, which can be directionally stabilizing. So the Vmc for this factor is at its highest when the gear is up, and decreases when the gear is extended.
Extended flaps will increase both drag and lift. The increased drag from the extended flap behind the operating engine may tend to oppose the yawing motion of that engine, requiring less rudder to counteract that yaw. So Vmc will be lower with flaps extended, and higher with flaps retracted (the take-off position for this aircraft).
Philippines accident, similarities with the Ghatkopar accident
In the Philippines accident after takeoff while performing the right turn, the pilot requested for a re-land which was duly acknowledged but the ATC with instructions to cross behind traffic on short final Rwy 06 (a perpendicular international runway) and to confirm if experiencing difficulty. However, there was no more response from the pilot. From a level flight southward at about 200 feet AGL, three (3) loud sputtering/burst sounds coming from the aircraft were heard (by people on the ground) then the aircraft was observed making a left turn that progressed into a steep bank and roll-over on a dive.
Left Hand Engine damage
The damage to the CT blades is due to overload and the same is mentioned in the investigation report. Similarly, the left hand engine power turbine blades are also damaged due to the debris passing through. There are clear indications of over temperature on the right side. The engine fire warning after which it was decided to turn back was most likely due to the engine damage. The report admits both engines suffered due to overload but concludes that there was no pre-impact anomalies.
Pratt & Whitney had issued a Service Information Bulletin on Compressor Turbine Blade Fratures which confirms the anomaly.
mindFly Probable cause in the Ghatkopar accident
- the loss of thrust on the Right Engine (recorded in the CVR)
- as per the wreckage, aircraft flap configuration at the time of the accident was landing gear down and Flaps Zero. The crew could have selected Flap Zero flaps for approach due to a possible thrust issue with the Right Hand(RH) Engine, to minimise drag(LH engine had a FIRE indication previously). If a breakout manoeuvre was to be performed, there would be a significant level segment.
- during the approach, the Thrust on the RH Engine reduced as per the CVR conversation between the crew.“Now RH engine is not giving power….Right?, Yes Sir”. This “NOW”could mean that previously Left hand engine was developing less thrust and was not operating with reduced thrust. Photographs of the left engine Compressor turbine & Power Turbine clearly show damage to the blades and signs of over temperature. The report states that both the engines suffered damage due to overload but contradicts at the end by stating that there was no pre-impact anomaly.
- ATC had asked them to increase speed by 20kts but they refused citing rain as a reason. Probably the engines weren’t developing sufficient thrust and that they didn’t want to disclose
- the VMCA and Stall speed with Zero Flaps is higher than with Flaps Down.
- the VMCA decreases with landing gear extension.
- as shown in the graph above, the drag of a windmilling(unfeathered) engine is significantly higher and requires more thrust.
- the VMCA with one engine inoperative(windmilling) is 6 kts higher as compared to both engines running.
- with the loss of thrust on RH engine, the speed may have dropped towards VMCA and the Co-Pilot called out “Speed”, at the same time the VMCA with a failed engine increases in a windmilling condition. Therefore, the aircraft may have been below VMCA in this configuration.
- as the Crew turned right for the break out procedure, the stalling speed, VMCA increased in clean configuration, with landing gear down. The speed breached the VMCA and similar to the Philippines accident the aircraft went into an instant catastrophic nose dive.
- there was no recovery time due to low altitude.
Key evidence not used optimally
The CVR records the flight crew’s voices, as well as other sounds inside the cockpit. The recorder’s “cockpit area microphone” is usually located on the overhead instrument panel between the two pilots. Sounds of interest to an investigator could be engine noise, stall warnings, landing gear extension and retraction, and other clicks and pops. From these sounds, parameters such as engine rpm, system failures, speed, and the time at which certain events occur can often be determined. Communications with Air Traffic Control, automated radio weather briefings, and conversation between the pilots and ground or cabin crew are also recorded.
- The conversation of the crew is not produced in the report verbatim.
- The tone of the crew is important to determine the situation inside the aircraft
- The conversation of the other personnel on board has not been produced
- Engine noise can indicate power/thrust levels
- Warnings/Cautions and other indications have not been recorded in the report
- Use of checklist, operation of switches and other background noise can be used as vital information for investigation
Practice of trivializing incidents, the latent threat
The regulator has been involved in trivializing accident to downgrade them to just incidents/minor incident. This change in nomenclature has legal and monetary ramifications. The current head of safety at the regulator, in 2010 was removed from his position when a probe into accidents/incidents were rejected for being misleading. The regulator had to remove the reports from their website.
The King Air C90 was involved in an accident while landing at Allahabad airport in 2008. The occurrence was termed as an ‘minor’ by the regulator instead of a ‘accident’ which it qualifies for as per ICAO/DGCA classification. As per the Ghatkopar accident report, the occurrence in 2008 was a serious incident whereas the damages to the structure and the statement recorded in the standing parliamentary committee on labour, report, state that the C of A was cancelled which is done post a serious incident affecting the structure of the aircraft. A cancelled C of A requires a special permit and greater scrutiny by the regulator prior to the revalidation test flight. Through this clever wording of a previous occurrence, the whole scrutiny & approval process by the regulator was avoided.
The agencies informed the Committee that the particular
aircraft was grounded due to an accident in February 2008 whose C of A
(Certificate of Airworthiness) was cancelled and was repaired in nonscientific manner and was taken for test flight without getting
completion/final certificate from DGCA is nothing but criminal
negligence which resulted into death of five employees/people.
The following was recorded by the committee too, “The information which came out about the horrible non-transparency/manipulation which resulted into accident of a private aircraft on 28.06.18 is an eye opener”.
Role of the regulator
The approval of the Air Operator Permit and the Operations manual without mandatory requirements being fulfilled points to a collusion between the operator and regulator &/or the intervention of the so called in the current setup “consultants”. These consultants allegedly present documentation in standard format to the regulator on behalf of the operator and help expedite the approval process of the permit.
The approval of A.O.P. is given after filling all checklists to the satisfaction of the team headed by the POI from the flight standards department, a flight inspector, airworthiness, safety, etc. The final sign off is given by the Director General.
The that question arises here is, why did these people involved in the approval process oblige and show utter disregard for the regulations? The same practice would have been adopted for other operators too. This is despite the fact that all operators were made to undergo the full CAP3100 approval process before FAA came in to audit the regulator after having been downgraded to CAT II.
UY aviation, the operator did not have a Chief of Flight Safety till the date of the accident as pointed out in the final investigation report. Other observations which confirm the assumption of a cosy relationship are that non-conformities pointed out in various audits were closed without compliance at the ground level. None of the audits pointed to the lack of DGCA approved post holder.
Former head of the regulatory body was the then director of the maintenance organistion. Therefore his influence or absence of oversight and ease of approvals can be explained by his presence. Critical task work as issued by the OEM were approved by the regulator without independent inspection or re-inspection.
The Quality department of IAPL had not carried out any audit during the 4 years that the aircraft was in their possession for maintenance. The reports points out that the maintenance organisation and operators manuals were not compliant with the latest regulators civil aviation requirements.
The parliamentary committee on labour pointed out and concluded that “The agencies informed the Committee that the particular aircraft was grounded due to an accident in February 2008 whose C of A (Certificate of Airworthiness) was cancelled and was repaired in nonscientific manner and was taken for test flight without getting completion/final certificate from DGCA is nothing but criminal negligence which resulted into death of five employees/people”.
The investigation needs to go deeper into every aspect and the possibility of criminal negligence must be investigated. The accident must therefore be investigated by a court of inquiry headed by a Judge who can then look at other aspects like collusion and financial dealings.
The report contradicts it self in two critical areas that of damage to engine and probable cause.
All the operators were re-approved prior to FAA’s visit following India’s downgrade to CAT II. This operator’s anomaly was still not highlighted.
Its 10 years after the Mangalore accident and a number of accident recommendations have not yet been implemented/accepted by the regulator. It was with great gusto that a cleanup act was initiated to improve the regulatory system and bring it up to speed with global standards but it soon lost steam and the malpractices soon engulfed the system rendering the aviation watchdog toothless.