Helicopter down outside Leicester City Football Club

[RVDT]

Further to OPR's comments -

Certification Specifications contain the following statement -

Fasteners

(a) Each removable bolt, screw, nut, pin or other fastener whose loss could jeopardise the safe operation of the rotorcraft must incorporate two separate locking devices.
The fastener and its locking devices may not be adversely affected by the environmental conditions associated with the particular installation.

(b) No self-locking nut may be used on any bolt subject to rotation in operation unless a non-friction locking device is used in addition to the self-locking device.

At the outset this seems to be prudent and simple but there are other subtleties. Installation of locking devices implies that someone has made the effort to install things correctly and
when doing a "duplicate inspection" the second inspector can at least see that the locking is in place.

As quoted by OPR the locking devices do NOT have anything to do with the integrity of the fastener. If the fastener has become loose and it is relying upon the locking device
something is wrong with the connection and the safety system works.

There are numerous issues that safety locking can overcome and incorrect torque is only one of them.

Incorrect hardware
Worn hardware
incorrect assembly of the fastener etc etc.

Nuts and bolts can be more complex than a lot of people appreciate.

I know of one particular large manufacturer who does not comply with the above statement but that is another story.......................

[Diesel_10]

FAA Follows EASA with Stricter AW169 Emergency AD

by Mark Huber
- November 9, 2018, 1:49 PMThe FAA has issued a more comprehensive Emergency Airworthiness Directive (AD 2018-23-52) to cover Leonardo AW169 and AW189 twin-engine helicopter tail rotor servo-actuator assemblies, following the issuance of an EASA Emergency AD earlier this week. The FAA said it “determined the unsafe condition exists and is likely to exist or develop on other helicopters of the same type design.”

The FAA Emergency AD requires inspecting the nut, cotter pin, lock-wire, hinge bracket connected to the tail rotor servo-actuator feedback lever link, and each connection of the tail rotor servo-actuator feedback lever link. It also requires applying a paint stripe or torque seal on the nut and reporting certain information to Leonardo.

The EASA AD specifies visually inspecting the nut, cotter pin, lock wire, and hinge bracket for condition and absence of damage, while the FAA Emergency AD requires inspecting those parts for correct installation and loose, broken, and missing parts. While the EASA AD specifies visually inspecting the connection elements of the tail rotor servo-actuator feedback lever link, the FAA Emergency AD requires inspecting all three connections of the tail rotor servo-actuator feedback lever link for correct installation and loose, broken, and missing parts. The inspections specified by the FAA Emergency AD are not limited to visual inspections.

The EASA AD requires contacting Leonardo for approved instructions if there is any damage or other finding, while the FAA Emergency AD requires performing any necessary repairs in accordance with FAA-approved procedures. The FAA AD covers seven helicopters on the FAA registry and estimates the cost of compliance at $255 per helicopter. Leonardo has produced approximately 70 AW169s and 55 AW189s to date.

[212man]

No real news but AAIB special bulletin....
https://assets.publishing.service.go...018_G-VSKP.pdf

[beamender99]

The helicopter ....... did not respond to the pilot's command, initial findings show.

https://www.bbc.co.uk/news/uk-englan...shire-46208494

[CyclicRick]

BBC news just posting that the "helicopter did not respond to pedal inputs".
Beat me to it.

[DOUBLE BOGEY]

Its is interesting that the Landing Gear was retracted! On a structure RFM profile should this not be done at Vy + 200 feet?
The aircraft impacted upright. If the gear was down maybe some energy would have been absorbed......maybe it would not have rolled!

[GrayHorizonsHeli]

I think landing on the stone wall/fence was the deciding factor to the aircrafts eventual resting place, regardless of gear up or down.

[Sir Niall Dementia]

Originally Posted by GrayHorizonsHeli

I think landing on the stone wall/fence was the deciding factor to the aircrafts eventual resting place, regardless of gear up or down.

And the gear speed restrictions tend to make most people hoik it up pretty quick.

SND

[212man]

And the gear speed restrictions tend to make most people hoik it up pretty quick

Interesting, as without doors you would not associate that kind of gear with a IAS low restriction - is it because it's electrically actuated?

[asdf1234]

Interesting that after loss of TR authority, the aircraft continued to climb. Why would the pilot increase the power when he lost the TR?

[212man]

Originally Posted by asdf1234

Interesting that after loss of TR authority, the aircraft continued to climb. Why would the pilot increase the power when he lost the TR?

I would guess at an involuntarily input caused by either the startle factor or bio-mechanical due to the sudden forces being experienced. It wasn't much.

[Fareastdriver]

involuntarily input caused by either the startle factor

Who was actually flying it?

[G0ULI]

Fareastdriver

Given that the AAIB report refers to four passengers and one pilot, and states that the aircraft failed to respond to the pilot's pedal inputs, the answer is obvious.

[dClbydalpha]

Originally Posted by asdf1234

Interesting that after loss of TR authority, the aircraft continued to climb. Why would the pilot increase the power when he lost the TR?

I'd assumed that collective increase was part of the initiation of the next manoeuvre and was accompanied by a pedal input to anticipate the increase in torque. In this case only one happened and the aircraft climbed for a short time.

[asdf1234]

Originally Posted by dClbydalpha

I'd assumed that collective increase was part of the initiation of the next manoeuvre and was accompanied by a pedal input to anticipate the increase in torque. In this case only one happened and the aircraft climbed for a short time.

The AAIB reports are always concise in their use of language and never leave room for ambiguity of interpretation. If the climb was as a result of the transition procedure they would either omit the climb event or positively correlate the climb to the transition procedure . They mention the climb subsequent to the TR loss of authority because it is an event of interest to them .

​​​

[Cows getting bigger]

Indeed. They do not mention a "collective increase", they merely state that the climb paused and then continued. There is implication that the pause was coincident with pedal movements and associated (correct) yaw which then became yaw that did not reflect the pedal demand.

Head scratch moment - if the tail rotor demand reduces, the system sends more to the main rotor. Remember the collective/pedal interaction?

[dClbydalpha]

Originally Posted by Cows getting bigger

Indeed. They do not mention a "collective increase", they merely state that the climb paused and then continued. There is implication that the pause was coincident with pedal movements and associated (correct) yaw which then became yaw that did not reflect the pedal demand.

Head scratch moment - if the tail rotor demand reduces, the system sends more to the main rotor. Remember the collective/pedal interaction?

They don't mention collective at all, but there must have been some at some point.

Rather than deduce the pilot was "startled" does it make more sense that the climb was due to a pre-planned manouevre? One which required the application of collective, but was aborted due to the lack of yaw control? How long would it take for him to realise he didn't have yaw control, does this amount to about 100ft?

What feedback would cause loss of tail rotor to send more to the main rotor? Are you thinking an automatic increase in collective pitch, or an ungoverened increase in Nr?

[DOUBLE BOGEY]

Originally Posted by dClbydalpha

T
What feedback would cause loss of tail rotor to send more to the main rotor? Are you thinking an automatic increase in collective pitch, or an ungoverened increase in Nr?

I feel this is dead herring!

If the TR Pitch reduces (reduction of effective thrust) drag reduces accordingly. This would momentarily cause the NR to increase as now power available exceeds power demand for Nr Nominal 100%. However, the FADECS would sort this out really quickly. In any case, a slight momentary increase in NR will not correspond to an immediate and somewhat sustained climb.

Other than that I cannot see any other correlation between the Yaw Channel (failed) and the collective moving involuntarily unless the mixing unit was somehow stuffed.

[RVDT]

However, the FADECS would sort this out really quickly.

Or maybe not - appreciate that the FADEC has inputs from control positions i.e. collective and TR pitch, torque, and atmospheric data and that is mapped inside the ECU to a fuel flow required to achieve the net result.

Actual speed governing might not be a good as "normal" if you had a full left pedal input to the ECU with no resulting increase Q load from the TR would probably give you an unintended result.

NR is normally referenced to the current DA and speed is governed by pre-empting the relationship between CLP and TR pitch. Quite often with CLP and TR pitch inputs are attached to either end of an LVDT (Linear Variable Displacement Transducer) and this value via the map in the ECU will give you a fuel flow pretty close to that required without being reactive to a change in NR.

Current FADEC controlled engines are great. They are also great at masking the true characteristics of the main rotor. When the FADEC is removed from the loop (autorotation) many are surprised at how "lively" the main rotor is to RPM. control.

Loss of input data will normally give you a "DEGRADE" warning but more likely not in this case.

[helicrazi]

Who has tried this profile in the sim yet with a TR failure at the same point?

anyone get away without a red screen?