Careflight - Darwin AW139 Incident.

[Unregistered_]

CareFlight helicopter in 'serious incident' during Darwin rescue operation, prompting investigations - ABC News (Australian Broadcasting Corporation) (http://www.abc.net.au/news/2018-05-22/careflight-helicopter-loses-control-during-search-rescue-atsb/9786298)

[rrekn]

Sounds like an AP disconnect issue. Well known in the AW139 and should be corrected with BT 139-500.

[NRDK]

Whether AP disconnect or not, clearly the cockpit acknowledgement of modes engaged and subsequent monitoring of the aircraft flight path degraded. The Spanish accident sadly another example.

[gulliBell]

I didn't read much in it. There was a disturbance in the automation and the pilot took corrective action. Did I miss something?

[Same again]

I understood that Careflight operated with 2 pilots? If so then NRDK is probably wondering why it took a 500 foot presumably uncontrolled descent to recognise that the auto-hover function was not engaged. It is usual for the flying pilot (once he has set the parameters) to request engagement by the non-flying pilot (or do it himself - particularly with hover mode on the cyclic) of the selected mode. This is verified by the other pilot who then declares that it is captured. Of course none of us were sat in the machine on that dark night so we are all armchair experts discussing a notoriously unreliable media report.

[industry insider]

Single Pilot with an “Assistant” apparently. All very safe and approved by the regulator of course. Nothing to see here.

[rotorspeed]

Same Again - surely whether single pilot or dual this is just dozey monitoring. Not exactly hard for an SP to check that any auto hover function is doing just that - well before a 500ft height loss. Another example of vulnerability of two crew ops - each relies on the other to do something important.

[[email protected]]

Were they expecting HVR to hold the height for them???? As I understand the system it needs either ALT or RHT engaged in the collective channel to do that, HVR only exists in the pitch and roll channels.

Reread the notes after Nescafe's post below and he is, of course, correct.

[Nescafe]

From the phase 7 notes

”At the engagement the HOV mode velocity references are set to zero. The engagement of HOV mode will automatically engage RHT mode if a valid radar altimeter signal is available and within the threshold limits.”

Then there is this.

”CAUTION
WHEN HOV MODE IS ENGAGED ABOVE 2000 FT AGL THE ALT MODE DOES NOT AUTOMATICALLY ENGAGE. THEREFORE THE PILOT MUST CONTROL COLLECTIVE MANUALLY OR ENGAGE ALT MODE.”

What height AGL were they when they engaged HOV?

[[email protected]]

Nescafe - it seems they were in a descent below 2000' so the RHT should have engaged but I can't find any RoD limits on RHT engagement which they might have been in excess of. Do you know what the threshold is for RHT (other than below 2000' and above 30')?

[Nescafe]

I can’t recall any vertical speed restriction with regard to RHT selection/operation, but that doesn’t mean there isn’t one!

[Scattercat]

I use this system regularly & over the years have found it to be generally quite reliable. It also gives you plenty of warning(s) if it's not functioning as requested or when you change a parameter. I always teach the importance of thoroughly understanding what you expect to see before selecting any mode / function and thereby you should be immediately aware of a problem. As others have said .... very close monitoring of the system and aircraft attitude is vital. I watch with interest to see what we can learn from what sounds like a close call.

[Jimmy.]

Tryed to upload the report, but something went wrong.
https://www.atsb.gov.au/publications/investigation_reports/2018/aair/ao-2018-039

[Jimmy.]

Tryed to upload the report, but something went wrong.
https://www.atsb.gov.au/publications/investigation_reports/2018/aair/ao-2018-039

Almost 2000ft ROD at low airspeed, recovery at 31ft AGL, 159,5% torque and a subsequent flight. I knew the 139 is a very powerful machine. Seems to be quite robust as well.

[belly tank]

Nescafe - it seems they were in a descent below 2000' so the RHT should have engaged but I can't find any RoD limits on RHT engagement which they might have been in excess of. Do you know what the threshold is for RHT (other than below 2000' and above 30')?

Hi Crab,

Minimum usage heights per supplement 34 is

For HOV:
Groundspeed less than 60 kts forward, less than 40 kts lateral or aft with IAS less than 75 KIAS and minimum usage height is 30’. :)

For RHT:
Airspeed range 0 to Vne
15 ft to 2000 ft AGL

Minimum usage height
150 ft AGL (airspeed
greater than 55 KIAS)
30 ft AGL in HOV (air-
speed less than 55 KIAS)

[[email protected]]

Belly Tank - I found those figures in the supplement but there is no max rate of descent for engagement which is what I was asking Nescafe

[212man]

Almost 2000ft ROD at low airspeed, recovery at 31ft AGL, 159,5% torque and a subsequent flight. I knew the 139 is a very powerful machine. Seems to be quite robust as well.
So they pulled 160% Tq, which would have generated a low Nr warning, and nobody suspected there may have been an RFM exceedence?

[Jimmy.]

So they pulled 160% Tq, which would have generated a low Nr warning, and nobody suspected there may have been an RFM exceedence?
From the report:
"At 2140:50, a yellow caution light illuminated and a crew alert system (CAS) message appeared on the display. Occupied with the recovery procedure, the pilot flew solely through the outside picture and the attitude indicator. The aircraft descended to a height of 31 ft AGL before attaining a positive rate of climb. As the pilot’s recovery manoeuvre ceased and control inputs returned to normal, the warning self-extinguished at 2140:57. The pilot noticed the warning, but could not read it before it extinguished.""A crew debrief took place and it was thought that a main gearbox overtorque could have occurred. There is no capacity in the aircraft for the crew to check for overtorque without the presence of an aircraft maintenance engineer (engineer). As a precaution, and as per Operations Manual requirements, the crew called a duty engineer to explain the situation and seek advice.

The duty engineer asked the crew to check the CAS system for messages. If an overtorque occurred, a white status message saying ‘maintenance’ would be present. This would signal a requirement to download and analyse data from the aircraft’s central maintenance computer (CMC).

The pilot estimated the extent of a potential overtorque to be within operational limits. The crew did not detect a maintenance message. With this information, the duty engineer advised that no maintenance activity was required."

Does the 139 have aural and/or visual alerts for low NR and overtorque (this one still lit after touchdown)?

[Hot_LZ]

The NR wouldn’t have drooped as the engines would just keep producing unless an TQ LIM was activated.

Regardless of the above you know when you’ve over torqued from a bad situation. Collective would be under your armpit and you’de see the ground coming at you! The maintenance message can be interrogated when you’re on the ground by crew or engineers. It’ll tell you in plain English that you over torqued!

LZ

[[email protected]]

the pilot flew solely through the outside picture and the attitude indicator. Not very good drills - if he need to be on instruments then he shouldn't be looking outside - if you are making an IMC recovery from what seems like an Unusual Attitude, it needs 100% focus on flying the instruments.

His mistake was to try and use the aircraft automatics to recover the descent which aggravated the situation - a simple go around would have prevented a potentially fatal descent into VRS.

Going back out again without having the aircraft checked seems a poor decision - sending a ground unit down to Salt Water Arm would have been a more grown up decision.

[212man]

The NR wouldn’t have drooped as the engines would just keep producing unless an TQ LIM was activated.

Regardless of the above you know when you’ve over torqued from a bad situation. Collective would be under your armpit and you’de see the ground coming at you! The maintenance message can be interrogated when you’re on the ground by crew or engineers. It’ll tell you in plain English that you over torqued!

LZ
Well max transient AEO Tq is 121% for 5 seconds. I've seen incidents with lower Tq with Nr droop

[Turkeyslapper]

Well max transient AEO Tq is 121% for 5 seconds. I've seen incidents with lower Tq with Nr droop

OEI MCP 140% 2.5 minute limit 160% .....near sea level AEO more than capable of getting to 159% without any NR bleed. Certainly seen that achieved in other parts of the world too 😎

[Torquetalk]

If 160% was pulled AEO, a red Inverted CAS message XSMN OVTQ should have displayed, then remained as red on black text in the CAS box. Hard to overlook.

Not sure Nr droop would be an issue, as each engine is still only supplying 80% of its rated power. This was an untidy go around AEO, not an OEI situation.

[212man]

My Nr comments are based on having seen FDM footage of a botched AEO go-around that used much less power, plus other incidents on other types but, if it didn’t drool, fair enough.

[Torquetalk]

My Nr comments are based on having seen FDM footage of a botched AEO go-around that used much less power, plus other incidents on other types but, if it didn’t drool, fair enough.

I have seen the opposite phenomena a few times, where most of the available power is used irrespective of weight, followed by an aggressive rotation in which the disk becomes offloaded briefly, accelerates and causes the EECs to chase the Nr. This can cause a transient overtorque. The cause may be a CAT Rambo profile..