Multi engine helicopters - Governor failure procedure

[Jelico]

Hi team,

On the hunt for some resources on procedures for governor/ECU failures in multi engine helicopters. Does anyone have anything available online they can recommend?

Also open to any useful tips of the trade that you might have. Understand some things are airframe specific, more looking for generalisations for light twins.

Cheers!

[Aucky]

Two simple general techniques beneath to kick off, for aircraft with manual backup in the event of a single governor/FCU failure. To my mind, the appropriate choice depends on what previous experience you have, how clear the cockpit indications are to easily differentiate between #1 and #2 engines, and whether the RFM specifies any differential TQ limits.

Note - before attempting either, make small collective inputs to ensure you have correctly identified which engine responds in TQ to collective inputs (automatically governed), and which does not (fixed/un-governed/manual).

1) Use manual control on the un-goverened engine to “match TQs” throughout (assuming TQ limited). This minimises the TQ differential between engines and if managed well reduces the likelihood of the automatically governed engine from approaching it’s upper or lower limits. However, the downsides are regular throttle inputs are required which can reduce capacity to fly a decent approach, which in turn may lead to larger collective/throttle inputs being required, exacerbating the problem. Also with both engine indications constantly moving there is the potential for inputs in response to the incorrect engine if the cockpit indications are not entirely clear which engine is in manual - these can be very confusing and rapidly lead to engines approaching limits.

2) set a nominal power on the manual engine appropriate to the phase of flight (low power for descent, mid power for cruise, higher power for climb), and allow the automatic engine to vary within it’s allowable limits for small fluctuations. Before lowering the collective to descend always roll off throttle a little, and never let the automatic engine reach <10% TQ, if it reaches 0% and you continue to lower the lever it cannot reduce TQ any less, and the reduction in drag from pitch reduction will lead to an engine/Nr over speed (or perhaps activation of the over speed protection circuit if fitted).

To a great degree the manner in which the approach is flown is more important to the outcome than excellent throttle control. My advice is fly a slightly shallow and slow approach. One really common error is over concentrating on the throttle control and being fast or steep at the end of the approach. Either case leads to larger than normal collective inputs which in turn requires corresponding throttle inputs. If you fly a slow and slightly shallow, constant angle approach, and get on the low speed side of the ‘power required for level flight’ curve early (generally <40-50kts by approximately 300ft) then throughout the remainder of the approach you progressively lose translational lift, meaning incremental small increases in collective and throttle until close to hover power is achieved which makes life very easy. Personally I try to keep the manual engine TQ just beneath that of the automatic engine when approaching the hover but that’s just preference for uniformity in indications. The single most common way to make life hard is to end up fast, with a flare at the bottom (large lowering of the collective), followed immediately by a rapid loss of translational lift leading to a large raising of the collective - avoid doing this...

[gulliBell]

My advice is:

1. read the procedure for this malfunction in the RFM, and
2. do what it says.

Then you can't go wrong. Problems arise when pilots think they know better and do something else.

With redundant digital engine controls in modern helicopters being so reliable, the chances of this malfunction happening are virtually zero. Whether you have a digital engine control or hydro-mechanical, the initial action is always the same. Keep flying. Collective follows the NR. If the NR is going high/low, follow it with collective. There is no real urgency to deal with this malfunction if the NR is maintained within limits.

[SARWannabe]

My advice is:

1. read the procedure for this malfunction in the RFM, and
2. do what it says.

Then you can't go wrong. Problems arise when pilots think they know better and do something else.



I think that’s a given, for anyone with any airmanship. The problem I think Jelico is alluding to is that usually the RFM doesn’t give you any advice on technique for manual flight other than to ‘remain within limits’. You can make it hard for yourself, or easy for yourself depending how you are taught, and what techniques you use to remain within limits. I surmise Jelico refers to light twins which don’t have dual redundant fadec control: AS355, A109, EC135, MD902. Not many in that category do except the very latest variants, and the RFMs don’t give you any advice on technique. It is for instructors to teach the best practices, and to ensure the RFM procedures are handled. Jelico my advice, ask questions, take what you will from it, but above all else, fly with good instructors who can tell you how best to achieve the intent of the RFM.

[SASless]

Most RFM's are edited by Lawyers whose job is to protect the builder of the Aircraft thus they limit the RFM to that required to deal with the immediate failure.

The Airmanship part should come from the Training Department of the Operator and by means of hands on experience.

The danger of SOP's is they oft times try a one size fits all approach to things and begin to create "Cook Book" styles of flying.

Most good Cooks pull from many recipes to find the one that works for them.

We shall see that demonstrated here as folks post their ideas....most all of which work....but differ slightly.

An example....in general I agree with Aucky....but differ to the extent I leave the Torque Meter and Collective following Nr till after I do my initial assessment which is simple.....is the Nr higher or lower than previously set by the Pilot.

If the Nr is lower...sssuming the clollective has not been moved following the failure....then the low side engine is the. problem.....and if the Nr is higher....then it is the high side engine that is the problem.

Next step is to control Nr if it is outside normal limits.

Then I go to the N1/Ng to determine if the suspect engine is within normal governing range or at or below Flight Idle range.....that determines if it is a governor problem or a engine failure.

Other indications like exhaust gas temp, oil pressure, oil temp, are secondary indications.

Torque needles alone tell you squat....as they will always be one high and one low but don't tell you the actual cause....but they will tell you which engine is responding to Collective Movement....which I use as a confirming method rather than an initial method.

I always felt that if you had time. enough to get scared....you had no reason to be scared....and thus no need to get in a hurry.

The fright of my life due to an engine problem was in an empty Chinook...low on fuel...in cool air....with one engine running away high that would not respond to normal methods....and due to the high Rotor RPM (like way high....blade slinging kind of high)....and the Thrust Lever (Collective) tucked right up under my arm. to try to control the Rotor RPM....and thus adding the good engine power to the combination....it was hard to determine what was going on as BOTH Torque needles were almost matched. It took looking at. the N1 gauges and seeing one engine way beyond Topping Limits and the other within normal governing limits that allowed us to identify the failed engine and be able to shut off the fuel to it....and regain control of the aircraft.

We whizzed through a cloud layer like a Rocket headed to the Moon with the rate of climb that produced.

Once we were flying on the one engine...we made a normal recovery to the airfield and taxied to parking.....my evening case of beer tasted good that night.

[Aucky]

Yes very fair point SASless. I was looking at it from a stuck/fixed governor perspective where the first thing you will see is a TQ mismatch caused by lever inputs, as opposed to run away up/down leading to an Nr change without collective input highlighting there is no one size fits all approach, but your Nr first (and comparison against high/low engine) does make absolute sense.

To diagnose any situation accurately requires a comprehensive understanding of the potential variables which is why I support Jelico’s curiosity, particularly as he has identified he is looking for ‘generalisations’. Whilst we can’t give a ‘this is what you do’, I think it is useful to hypothesise on some basic considerations which may make the RFM instructions easier to adhere to, and form part of the discussion with the instructor who is teaching you the type specific considerations.

[gulliBell]

Enough detail here to steer you in the right direction....


https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/597x767/screen_shot_2021_06_02_at_22_32_12_38d7b869547d704c4715314f3 137eeaedde1d540.png

[gulliBell]

..I was looking at it from a stuck/fixed governor perspective where the first thing you will see is a TQ mismatch caused by lever inputs...

With a digital engine control, such as in the S76C++, the first thing you will see is the blue DECU capsule light come on. This will remove power to the stepper motor in the fuel control unit resulting in a fixed fuel flow for that engine irrespective of collective position. Changing the collective position will now cause a torque mismatch. Although there could be a malfunction causing the stepper motor to go full open and things can then get exciting quickly, particularly if the collective position had a low power demand when the malfunction occurred.

If we had a very competent pilot in the simulator and he wanted a challenge to fill in some idle time, double DECU failure did the trick, one just after the other. i.e. both engines in manual fuel control. That malfunction would never happen for real, but it is covered in the RFM. It's a good challenge for the pilot to find a way to land without over spinning something.

[212man]

the Thrust Lever (Collective) tucked right up under my arm. to try to control the Rotor RPM....and thus adding the good engine power to the combination.
How does that work then?

In addition to the above replies, remember to not lower the collective in a rush with relief once on the ground, or it tends to negate all the work you just did! I have seen an FDM trace of a flight with a stuck governor, where they spent over 2 min on the ground at 106% Nr after landing, and needed an engine change......

I had an incident, that SAS will sympathise with, where I was sitting on the ground in a B212 waiting for some client managers to board from their houses, in an estate about 25 min from our main base, when I had a runaway up. I closed both throttles immediately and was about to open the Idle Stop to close them completely (per ECL), when I realised that the engines had responded and were now at IDLE Ng - thereby telling me it was an Nf governor failure and not Ng. To assist with trouble shooting for the engineers, I slowly opened each throttle in turn to what should be the governed Nf/Nr range, to see which behaved itself and , sure enough, one throttle maintained 100% Nf/Nr when it continued to be opened, and the other just kept taking the Nf/Nr with it. So I shutdown and called base to say "Number 2 Nf governor failure" and in due course the engineer flew in and replaced it and we flew home. Cue bollocking for not following the ECL to the letter.......(i.e not opening the IDLE stop and shutting down during the run up!)

[Sir Korsky]

If you got a wild engine, as soon as you've found out which one it is and you're capable of single engine flight, idle it, don't touch it again and find a nice runway to run onto. All the pissing around in the SIM that I've struggled with over the years to try and deal with the situation is more pain than it's worth. Fly the damn thing to somewhere safe and land. 100 miles out at sea yeah I know.

[SASless]

212Man.....contradictions abound in that far off Centre of Excellenc don't they.

I had a Generator Light on an engine....and per the ECL...I was to turn that Generator Off and then shutdown the engine....which I did per the Checklist despite my gut feeling that there was no reason under the Sun for doing that.

Somehow...some Sky God in the lofty realms of the main Centre of Excellence had ordained that be the procedure due to some bad Generator Bearings somewhere in the World.

I got challenged by a lesser Sky God for following the ECL

So....I would suggest we broke even between us.

Do you recall the Pilot that had a high side governor failure at a hover at the Warri IA who set the aircraft down all the while with the throttle full on....and the rotor blades making a really unhealthy din and finally got around to rolling the throttles off.....then who rolled the throttles back on and repeated that bit of wonderful airmanship?






Aucky....your point about the stuck governor is absolutely correct....moving the Collective (or in the Chinook the "Thrust Lever") instantly identifies the bad engine.

You noted I use that same collective movement to confirm my analysis after going through my routine.

I have seen lots of flights cut short in the Sim after the wrong engine was shutdown or the wrong fuel valves moved....or fuel pumps shut off while at an altitude too high to do without them.

That is why I advocate not doing anything beyond what is absolutely required to regain control of the Nr..

Helicopter Pilots live or die because of Nr.

[ShyTorque]

I used to teach my students to say “Engine malfunction” rather than “Engine failure”, to prevent adrenaline taking over before correct diagnosis of the problem.

As per SASless wrote, Immediate Actions should be:
1) Check and note the Nr...high or low? Correct as required with collective.
2) Raise and lower the lever .... which engine/s respond correctly.
3) Only then think about moving ECLs!

In the simulator (Puma) I once gave a student what was only going to be a spurious engine fire warning light whilst downwind in the circuit. All he had to do was confirm no signs of fire and continue to land. He overreacted by dumping the collective well below what was needed for single engined flight. He then looked at the Ng’s. Because he had dumped the collective and flared, both engines were backing right off, as advertised.

He then declared a double engine failure, shut down both engines and crashed!

Another, more senior student consistently misdiagnosed engine malfunctions. Quite worrying because he was a fairly experienced pilot, about to start a third tour and was refreshing on type. That was one occasion where the “record and playback” facility proved very useful....without it he would not have been convinced.

[albatross]

From old 212 daze:
High RPM High power on one engine = HIGH SIDE GOVERNOR FAILURE.
High Rotor RPM , High power on one engine, very low or even idle power on the other = High Side Gov failure on the high power engine. High power engine may not respond to throttle movement even if reduced to idle and you will have either shut down the high power engine or select manual governor as per the RFM ECL. NB. Do not select manual gov except when the throttle is on the idle stop.
In both cases Rotor RPM control is the first priority.


Low RPM low power on one engine = LOW SIDE GOVERNOR FAILURE.
Low Rotor RPM with high power demand on one engine and low power on the other = Low side governor failure on the low power engine. Reduce throttle to idle and select manual governor on the low power engine as per RFM ECL. NB. Do not select manual gov except when the throttle is on the idle stop..
In both cases Rotor RPM control is the first priority.
Once on the ground DO NOT lower the collective immediately as you may massively overspeed the rotor system. Best to set idle N1 on the failed engine or even shut it down before lowering the collective. Proceed slowly and think about what you are doing.

[megan]

Things don't always occur by the book.

S-76A - during flight the engines started waving hands over a large range, as one went up the other went down and immediately reverse, Nr rock solid. Determined which engine was the rouge and pulled throttle out of governing range, all settled down and returned home for maintenance. Later in the day scheduled for same aircraft, after 40 minutes of flight one engine dropped to zero TQ, reduced collective to contain the good one and was in the process of reaching up to pull the throttle when with the snap of the fingers the engine went from zero TQ to max and attendant overspeed of Nr. As the hand was about three inches from the throttle when this occurred the pull collective to contain was out the window and completed the throttle pull. Snapped governor drive shaft, maintenance had done an hour flight in the aircraft and being unable to fault put it back on line after the initial problem.

[gulliBell]

Things don't always occur by the book..

That's right. And not all malfunctions are covered in the RFM. In the C++ for engine oscillation malfunctions there is very scant information, pilot initiative is relied on to deal with it. Which is unfortunate in a "culturally aware" context because, unless it's written in the book some pilots have absolutely no idea what to do. Not doing anything and landing with oscillating engines will result in interesting outcomes.

[SASless]

...unless it's written in the book some pilots have absolutely no idea what to do.



Are you suggesting there are "Cook Book" Pilots out there somewhere?

[[email protected]]

Snapped governor drive shaft, maintenance had done an hour flight in the aircraft and being unable to fault put it back on line after the initial problem. Ah, the old 'System tested, no fault found' attitude beloved of many maintainers.............

[gulliBell]

Are you suggesting there are "Cook Book" Pilots out there somewhere?

Regrettably there are a few pilots out there who can't even find the correct malfunction in the book (those mostly being where English is not their first language). Which can be less desirable launching into the wrong checklist than doing nothing at all. Getting on the right checklist can be an accomplishment. And if the malfunction isn't in the checklist, they will keep looking for it in the checklist until they eventually arrive at the scene of the accident. Particularly that engine oscillations malfunction because the book only gives basic guidance and you need to cook up a sensible plan to deal with it. Without having a good systems knowledge and a cook book to rely on the cooked up recipe can get mysterious.

[SASless]

We once had a semi-retired Hangar Queen transferred to our unit after it had been cannibalized for spare parts until our supply system caught up with demand.

Our mechanics (Engineers to the not. knowing) put her together again and off we went to do air tests....job done and she was put to work with the other Fifteen assigned aircraft.

Each time she went out....if she went Northwest towards the Cambodian Border and Indian Country....one of the engines would fix at a low power setting and nothing would cure the problem....go anywhere else and she worked fine. (I am not making this up.)

Everything she was returned for maintenance action....with air tests....no fault found was the result.

This went on for a month....and sure as houses...if she went Northwest...back she came.....with different crews each time (we thought it might be a crew issue.....).

One day...one of the mechanics being a brighter spark than most but who was guilty of the greatest Sin in the. military....being an independent thinker...upon reflection and much study of the Maintenance manual started chasing wires...wire bundles...and connectors for the various engine control systems.

One the "good engine" side...he found a pin pushed back on a connector on the a system that had to do with both engines....not just each engine....and just like that....the old girl was able to go to t he Northwest again.

Only the Gremlins know why it was only flying to the Northwest that had to do with the problem....them being the sneaky rascals they are.

They were undone by a Technician that knew what he was doing and would not give up until he found the fault.

[megan]

Ah, the old 'System tested, no fault found' attitude beloved of many maintainers.........crab, I must confess I wouldn't necessarily point the finger at the maintainers, we lived professionally beneath a mushroom, no intercourse was permitted with entities outside of our own few acres of dirt. When the 76's were purchased the C & T was sent to the US for endorsement and he was to come back to endorse we lower ranks, he suggested to the company that he stop over for a day or two at one of his transit points to chat with an established 76 operation, he was told that under no circumstance was he to make contact with said organisation. We saw it as the aviation advisor protecting his little patch/empire, nor did anyone, other than the advisor, ever attended international forums, just not done old boy. Engineers were under the same restraints, once they were licensed that was the end of any education, most were actually unlicensed, budget you know, you have to pay extra for licensed, the licensed signed off on the work done by the unlicensed. The biggest fracas I ever saw was a pilot came back with an aircraft that failed the trend by a monumental margin, engineers decided a ground run was in order and during the check the engine self destructed big time. I wonder if the trend was trying to say something?

[SASless]

I wonder if the trend was trying to say something?

Hey young fella....you have to admit the Trend remained constant after the ground run....and did not get any worse did it?

Cheap hired help....pooh!

I bet your Management did not buy cheap unchangeable tickets and charge the Client for full fare tickets...and then pocket the difference....or use any air miles accrued by Staff Travel for their own personal upgrades!

The Owner was quoted by some as having said (no idea as to the truth of that statement)....."If my Chief Pilots will not steal from me....they will not steal for me!".

[megan]

I bet your Management did not buy cheap unchangeable tickets and charge the Client for full fare ticketsWe didn't have a client SAS, we were employees of the oil company. Funny thing about staff travel, aviation advisor reported to the company that he saw no value in sim training, when pressed the company quibbled about the cost, company policy was that overseas travel was to be first class, we said that we would travel cattle class if cost was an issue, but the company declined the offer because that would have set a precedent to the perks that they, the managers, took full advantage of. In the wash the company relented to sim every two years for captains, co-pilots nothing. I must admit though it was extremely onerous travel, crossing the pacific dressed in pajamas and sleeping horizontal in a bed at 30 something thousand feet, we learnt what a tough life our managers had, our hearts bled for them for the privations they suffered.

[gulliBell]

.....The biggest fracas I ever saw was a pilot came back with an aircraft that failed the trend by a monumental margin, engineers decided a ground run was in order and during the check the engine self destructed big time....

Oh yeah, I remember that one well. I was the bunny who wrote the in-flight trend check numbers down that day (which was the SOP in that operation, outbound leg of first flight of the day the power trend check was done and recorded). When megan says failed the trend by a monumental margin, he's not exaggerating. The engine went from something like a +5 on trend the previous day to a -20 on that flight. Bunny hopped out on arrival back at base, engineer hopped in, started the hover power check. Kaboom. Engine exploded (an Allison 250-C30). From memory there was a video of all the excitement taken from the heliport tower showing the helicopter emerging from a cloud of blue smoke . What was left of that engine was written off.

[Viper 7]

I had a low side failure on the Sea King at sea about a thousand years ago.

Affected engine went to idle Ng and low Nf so it was easy to diagnose. Happily it was during the day and fine weather, so easy free deck landing. We burned some fuel off and practiced with the emergency throttle a bit then I had the FO fly for the landing as I “flew” the emergency throttle, keeping the affected engine about 20 percent Q behind the good engine. Just have to remember the Q goes down much quicker when the collective is lowered so you have to be brisk getting the Q down on the emergency throttle.

Had a FCU fail on the 412 too. We were practicing gov fail, rolled throttle down, checked idle numbers, etc with dual concurrence, flipped the gov switch to manual and the TOT went to 1000+ in about a second. Shut down and OEI approach back to pad. Visual insp, no damage to engine. FCU change. Only time I ever had a snag on the PT6. Well..except that time as an FO when it wouldn't start...until the tech came out and turned on the fuel switches....sigh. LOL

[gulliBell]

.. We were practicing gov fail, rolled throttle down, checked idle numbers, etc with dual concurrence, flipped the gov switch to manual and the TOT went to 1000+ in about a second...

Cut and paste as follows:

We were practicing gov fail hydraulics on/off, rolled throttle down full open, checked idle numbers, etc with dual concurrence, flipped the gov switch to manual and the TOT went to 1000+ in about a second..

[SASless]

Not that has ever happened before....or get the wrong governor switch.....sometimes you see what you expect to see....and other Dummy confirms you both are.

[212man]

Cut and paste as follows:

We were practicing gov fail hydraulics on/off, rolled throttle down full open, checked idle numbers, etc with dual concurrence, flipped the gov switch to manual and the TOT went to 1000+ in about a second..
Which is why Bristow moved the panel with the GOV switches to the other side of the centre console from the hydraulics panel. They also moved the TQ and Triple tacho gauges to the bottom right of the instrument panel - something weird to do with them being in the field of view during critical phases of flight, or something. Was entirely logical and based on experience, but made dealing with governor malfunctions in the (FSI) simulator interesting - couldn't find the damn gauges!

[SASless]

Moving the triple Tach had more to do with the Bristow Mod designed in their mind to prevent Loss of RPM actions.....part of which was disabling the Torque Limiting system...which also removed the Torque Damping which made Torque Control really dodgy...and led to lots of overtorques and a mod to the mod for a system to record overtorques.....and ultimately the whole mess was **** canned and the aircraft returned to Factory Spec.....as I recall it.

The moving of the control panel was done by other operators as well....not just Bristow.

I do not know of another Operator who used any such Mod as the Bristow Torque thing.

[212man]

Moving the triple Tach had more to do with the Bristow Mod designed in their mind to prevent Loss of RPM actions.....part of which was disabling the Torque Limiting system...which also removed the Torque Damping which made Torque Control really dodgy...and led to lots of overtorques and a mod to the mod for a system to record overtorques.....and ultimately the whole mess was **** canned and the aircraft returned to Factory Spec.....as I recall it.

The moving of the control panel was done by other operators as well....not just Bristow.

I do not know of another Operator who used any such Mod as the Bristow Torque thing.
I'm sure other operators will have moved the panel - it certainly made no sense ergonomically and the mistake described is very expensive!

The Bristow Tq modification was a direct result of a fatal accident in the North Sea, which MAY have been averted if the factory standard system had not been designed to limit Tq to 104% - saving the MGB vs the airframe is maybe not the best design compromise. The UK AAIB recommended that it be investigated whether the Tq limiting be increased, and a recording device installed to record any overtorques. The limiting was not removed, but "wound up". Governor instability was a natural result and a recognised issue. Later in service they installed the 'Hi Power mod' (TB-138/145) with an increased TO Tq limit, and a trim actuator for No 2 Nf, using a beep switch on the collective to help match Tqs as they became unstable.

AAIB report here: https://assets.publishing.service.gov.uk/media/5422efd3ed915d1371000297/10-1982_G-BIJF.pdf

[SASless]

Reading the accident report reminds me of several things.....but lets focus on just one aspect of the crash.

The loss of rotor rpm figures in this.

212man explained the Bristow reaction and subsequent Mod to the 212 over concerns of rotor droop during an emergency.

So....212man......remind me of the Single Engine Procedures taught by Bristow and tested on Base Checks on the 212....where Pilots were taught to DROOP the Nr to gain maximum performance of the aircraft.....what was the Nr. number we used....was it 90 percent?

It was close to full up Collective .

That was for Engine Failure after TDP....with a continued Takeoff.

For those unfamiliar with Bristow's Base Check methods....the aircraft was always ballasted to approach something like 90-95% of Allowable Take Off Weight for that particular set of climatic conditions DA, etc.

That was for OEI but the Rotor doesn't know if there one or two engines driving it....it droops when there is not enough power being applied to the rotor to maintain the collective setting being applied.

There seems to be a contradiction there....droop it on one....and lets overtorue it on two but not droop it and accept the overtorques......no consistency in that

The other part of the Report that gets my attention....CFIT after Loss of Control after continuing to fly into IMC weather while trying to maintain surface contact visually.

That put the aircraft into an impossible position and it seems the AAIB and Bristow were looking for solutions for the wrong cause of the accident.

[ShyTorque]

On the Puma course, early stages, we used to teach a simple “70/30” approach to a landing in the event of an engine malfunction (very rare on a Turmo engine due to no electronics, they had purely mechanical centrifugal engine governors). Having recovered the Nr and with the faulty engine secured, fly a relatively shallow, trimmed approach at 70 kts to a firm surface. At approx 100 feet agl flare the aircraft to about ten degrees nose up, aiming to touch down at about 30kts (translational lift burble point).

It saved a whole lot of faffing about with throttles. There’s no reason why it shouldn’t work on almost any helicopter...certainly I’ve used it twice on an A109 (engine chip light induced shutdowns with diversion to an airfield).

[megan]

We had a chap caught out by the governor panel being positioned slightly different in the 212 and 412 centre console, one higher than the other. We operated both types, meant to grab the hydraulic and got the governor instead with predictable results. Not the first time some one has been caught out by aircraft having disparate set ups.

One interesting 212 failure by one operator was the practice of placing ones pencil on the centre console, chap lowered collective and an engine immediately went into manual. Pencil had vibrated out to be caught under the collective when it was lowered, edge of panel acted as a fulcrum, other end of pencil caught under the switch and lifted it out into manual.

[gulliBell]

..One interesting 212 failure by one operator was the practice of placing ones pencil on the centre console..
I can imagine that exactly as described. It would never occur to me as being a possibility otherwise.

[Ascend Charlie]

One interesting 212 failure by one operator was the practice of placing ones pencil on the centre console, chap lowered collective and an engine immediately went into manual. Pencil had vibrated out to be caught under the collective when it was lowered, edge of panel acted as a fulcrum, other end of pencil caught under the switch and lifted it out into manual.

In Vietnam in a Huey, a senior officer with nothing to do (cojo doing all the work) reaches over the console and selects GOV to MAN. With throttle full open, the aircraft leaps upwards, but being formation leader, the rest of the pack tries to follow him up. Then they have to rapidly reverse and try to follow him down, now that his turbine has burnt itself out and lost power. The Rubber Duck strikes again.

Senior officer claims he just picked up a clipboard to write something, and the string holding the pencil to the board must have caught the GOV switch. Yeah, not what the cojo saw.

[Jelico]

Thanks for everyones input. Obviously, flight manual procedures come first. I was looking for general input to put a presentation together on the subject. Have even had the pleasure of a high side gov failure in a 355 a few years back. I wanted to put some power points together on the general differences between transitioning from single engine helicopters to twins. Lots of resources available online and in the books/manuals on Cat A procedures, engine failures etc but very little on governor/ecu failures. My own experience was confusing, and presented very similar to an engine failure on the good engine. I guess I am looking for some good cheats, on the diagnosis side of things. One you've figured out what you're dealing with, training takes over and it is usually manageable - but it can be hard to figure out in the heat of the moment, along with the surprise and a few screaming pax mixed in.. Appreciate the posts, all useful for what I am trying to do. Thanks

[gulliBell]

...but it can be hard to figure out in the heat of the moment...

Modern digital engine controls will tell you which engine has the problem, not hard to figure out at all.

[Ascend Charlie]

I had a high-side governor failure on a BK117, at that time, the first one in Oz. None of us had flown twins, though we had thousands of hours in singles. The instructor was Japanese, and such things were never discussed.
I was in a high hover over trees when the alarm for a torque split sounded. Oh poo, can't hover, can't land, see if I can get some forward speed and fly away. Got to safety speed and climbing, look at the dials. One engine very low, one maintaining RRPM - but I didn't look closely enough at that dial, with adrenaline pounding and first ever apparent engine problem. Identify, verify, move roof-mounted throttle to idle.
Still flying. Hmm.. the "sick" engine is still running. Gently move throttle forward again, oops, high RRPM alarm. WTF?? OK, I am only 4 nm from the airport, fly it back, running landing on the grass, roll engines back to idle. All looks good. Advance "sick" engine - no problem. Advance "good" engine, RRPM go berserk again. Shut down.

A P2 line to the FCU failed, so the engine ran away high - safer than going low I suppose. But being alone in the front, I would have needed 2 hands on the throttles in the roof to manipulate the "good" back down to keep RRPM normal, and I needed one hand on the cyclic - no SAS, no autopilot, just raw inputs. No could do.

So, I learned something, and told the rest of the crews about it.

[gulliBell]

...I would have needed 2 hands on the throttles in the roof to manipulate the "good" back down to keep RRPM normal...
And there is another advantage of modern digital engine controls, you don't need to touch the engine levers for this malfunction...hands can stay on the controls.

[Nescafe]

The modern machines can introduce a bit of a ‘gotcha.’
The 139 with a high side run up can give you an OEI warning against the good engine, only because it has wound itself down to try to compensate for the high side failure. NR is the key to avoid getting distracted by the OEI symbology, and as mentioned previously, a little up/down on the collective to see which engine responds.

[megan]

High side failure at the worse time on a platform take off that resulted in ditching the 214ST. Lots and lots of lessons to be learnt.

https://www.atsb.gov.au/media/24790/199100020.pdf

[[email protected]]

As others have said - the clue is what the Nr is doing. If the Nr is lower than you would expect for that power setting, the low Tq engine is the problem - if the Nr is higher than you would expect, it is the high Tq engine.

Contain the Nr within limits using collective - this will also help you confirm your diagnosis.

If you can, establish safe single flight speed before doing anything with the engine controls.

When you do select and engine to turn off, only select it to idle to check you have A. correctly diagnosed the fault and B. actually selected the correct engine.

In the E Timor accident linked above - the Nr was higher than normal in the middle of a transition to forward flight - that immediately tells you high side runaway if the Nr goes up at a high power setting.

[SASless]

I have not flown the 214ST but have been at operations where they were flown....and my understanding is they will fly at max weight with only a single engine operating. (Someone might correct me if that perception is incorrect).

If that is the case...there should be no hurry to carry out any immediate acton beyond fly the machine and accelerate and climb away.

Analysis of the failure has to be done with the Power Setting at the time of the. failure....as altering the Collective Setting then checking Nr will only add to the difficulty of assessing what kind of failure you have.

In the linked Accident Report we see that happen.....moving the Collective.

The Co-Pilot did not correctly state the problem....which also added some confusion into the situation.

Neither Pilot got it right and fortunately no one got hurt but an aircraft got written off as a result.

What is shown is proper training (which the pilots had not had) is the key to success.

The decision to not send Pilots for Sim Training in the United States was based upon cost.....and I have to wonder how many trips to the States could have been done for the cost of replacing the damaged aircraft?

Was this another example of false economy?

We saw something similar in the Koby Bryant Crash.....the absence of Sim Training.

[JohnDixson]

High side failures in a twin engined machine have always been a challenge as described. Hopefully, the new dual Fadec designs will eliminate all but the fuel valve failing open. Perhaps someone from an engine manufacturer can address the news on that area.

[gulliBell]

The fuel valve failing open AND a high side governor failure? Glad you were never my sim instructor.

[SASless]

Gulli....in your time teaching in the Sim....how many well experienced Pilots were unable to cope with a High Governor Failure that did not respond to Throttle movement?

Never mind the added thrill of a failed fuel valve to boot!

[gulliBell]

Casting my eye over my training session notes, "DECU Hi" appears time and time again as problematic for many pilots to deal with. I see one note here where the pilot lowered the collective three times in a row in response to DECU Hi and the NR went off the dial. After being told that was the wrong thing to do, and why, and what he should have done, and then to be told we were going to repeat the exercise, and he did the same thing again. Unfortunately there just isn't enough time allocated to keep repeating the exercise until they get it right.

[JohnDixson]

GB, I wasn’t suggesting a dual simultaneous failure. I was merely explaining that once dual fadecs are on a given machine, the redundancy of sensors and processing eliminates all of the failure modes that could cause a high side governor ( I’mm pretty sure-but never say never in aviation ) except for the failure of the final metering valve. And again, the engine manufacturers may.may have introduced changes in that area to further mitigate aginst a high side/max fuel failure.

[gulliBell]

Yes, the redundancy is so redundant with dual digital electronic engine controls that the high side governor failure is extremely unlikely. I've never heard of it happening, but it is still in the RFM for the S76C++. However I am aware of real life DECU MAJOR malfunction where the fuel flow is fixed (in the position the fuel metering valve was in when the malfunction was sensed by the DECU). This is a more realistic training exercise in the simulator than doing the DECU hi-side. In recurrent training I would bring it on during the take-off roll before CDP (i.e. when the engines were at a high power setting). Crew response went one of two ways. More often than not the malfunction was not noticed by either pilot and they continued the take-off and climb out, despite a big blue warning light being on right in front of their eyes. The malfunction only being noticed when power was reduced when establishing cruise flight and the torque split becoming apparent. As long as the good engine is still delivering torque the NR will not increase. On the rare occasion the malfunction was noticed early the take-off would be rejected and land back on the runway, which is exactly the wrong thing to do. Because they lower the collective all the way at touch-down and the NR goes off the dial and there you have a needless $1M repair bill. When I hear a crew departure brief "any malfunction before CDP I'll reject back on to the runway" I will give them that malfunction and they will see why it is not a good idea to reject the take-off with a fixed high power setting. You need to keep flying, get a safe altitude, PNF get out the ECL and deal with the issue as written. It is a very easy malfunction to deal with, and an expensive one if you act in haste and mess it up.

[ShyTorque]

I will give them that malfunction and they will see why it is not a good idea to reject the take-off with a fixed high power setting. You need to keep flying, get a safe altitude, PNF get out the ECL and deal with the issue as written. It is a very easy malfunction to deal with, and an expensive one if you act in haste and mess it up.

Departing into a low overcast and encountering a high side failure....really not your day.

[[email protected]]

The venerable Wessex had electric fuel computers which would freeze the throttle actuator in the event of loss of signals (NF, N1 etc) but also if the battery voltage dropped below 18V if memory serves.

The problem was that once frozen, you could only recover the engine from it's frozen power level by bringing it back to idle.

Due to a series of electrical problems and a lack of a voltmeter, it was possible for a bad generator to drag the good one off line as well and result in rapidly falling battery voltage.

This led to a number of double computer freezes in tricky conditions.

We used to pull to just under max twin Tq on the first transition of the day and at that point, with a moderately low cloudbase, a colleague discovered that both had frozen and he was zooming skywards.

Fortunately he managed to get one back to idle and avoided IIMC but was till left with the other stuck at a high power setting.

[gulliBell]

Departing into a low overcast and encountering a high side failure....really not your day.

Departing into a low overcast even with everything working properly....regrettably the outcome can be ruinous of one's day. Fortunately the reset button can recover the ruins.

[ShyTorque]

gulliBell, unfortunately that reset button only works in the simulator!

[SASless]

Had that bit of fun....and whizzed through a layer like a rocket headed to Mars.....no sooner had looked in to get on instruments and we were back into the sunshine....pulling G's going UP!