Chip warnings

[Too Cloudy]

Rotorque,
There is a supplement in the flight manual of the BK117 that I have been flying recently that gives you the option of either shutting down the engine, which is what is written in part one....or retarding to flight idle as required and monitoring the systems and parameters. You then have the option of re-introducing the engine lever on final approach..or leaving it at flight idle and conducting a normal OEI approach.
Captains discretion.

[Devil 49]

Declare, or "PAN" for a chip light? With no secondaries? I guess I still don't get it.
I don't "declare" if I go around weather, or decide to land because of weather;
Or if the trip is taking longer than planned and requires a fuel stop;
Or a passenger gets queasy and everybody else looks like joining in;
Or a million other things that change your flight plan. If you have to use official status, (declare/PAN) to keep the situation from getting worse (feeling kind of nauseous yourself...), do so.
A chip light with no secondaries and a landing place within reasonable distance is a flight plan change, like the above.
But I'm not offshore right now, or over the mountains, or IFR, or...

[Lu Zuckerman]

Admittedly I cannot speak from a pilots perspective relative to what a pilot should or should not do regarding a chip light. However this thread keeps returning to what you would do if you have an engine chip light with most of the posts addressing helicopters with more than one engine. By definition on a dual engine helicopter or a helicopter with two power modules the engines / modules are redundant. This redundancy may not be apparent under certain conditions, as on occasion the second unit cannot maintain flight and the helicopter must land. However on a helicopter the transmission has no redundancy and that goes for the driveline as well. On a Boeing-Vertol tandem helicopter if one gearbox goes out for any reason all is lost and the same goes for a K-Max as well. Gearboxes can fail catastrophically without warning and in those cases a chip warning may not be indicated. This may have been the case with the Boeing-Vertol crash in the North Sea several years ago. In the illustration of the Italian SH3-D above the pilot got the warning and an instant later he got the failure. The EH-101 is designed to survive a total lock-up of the transmission but in the process may very well destroy much of the main rotor but that is a subject for another thread.

The reliability and survivability of a helicopter dynamic system and its’ driveline are a function of proper design, proper material selection, proper manufacturing, proper assembly and proper quality control and eventually proper maintenance. Every once in a while one of these elements will come into question and a failure will manifest itself. The extent of the failure and how it manifests itself is a crapshoot and your ultimate survivability of this failure is dependent upon your response to the warning. That is why the designer put chip lights on your instrument panel and to provide further protection they provide a press to test switch.

You have a choice. Respond to a chip light or be protected by an AD that modifies your transmission with this AD having been written in response to a catastrophic failure in which a helicopter and its’ crew were lost as a result of that pilot not responding to a chip light.

If I come across as a doomsayer that is the nature of the business I am in.

[Vfrpilotpb]

I would without fail, upon seeing or hearing a chip light warning, head quickly (hopefully under my control) to good old mother earth, on the way I would squeel like a stuck pig to the nearest ATC! Once on the ground, If able, I would then investigate what had caused my situation, and withdraw from my pocket the little black box, to summon help.



[ 04 January 2002: Message edited by: Vfrpilotpb ]</p>

[U R NumberOne]

I think the most critical aspect of our operation with respect to chip warnings is the fact it is over the North Sea, where landfall can be one hour or more away and who knows which helidecks in your vicinity are available for a landing. So generally, the option is a return to Aberdeen, Sumburgh/Scatsta etc, but the biggest variable is the classification of the problem.

Reading some of the previous posts, the chip warning light is taken extremely seriously, which just makes us even more curious about the variation in some North Sea crews declaring the problem. Unfortunately such complacency by crews can impact on ATCOs (especially the younger generation) who may start to treat such problems as complete non-events, when there may be a lot more to the situation than we are told about.

[ShyTorque]

Devil 49,

I would put forward that the advice you are offering regarding the seriousness of a chip warning is dependent on aircraft type and the associated RFM.

For one aircraft I fly, the RFM tells the pilot to close down the engine in the event of an ENG chip light, full stop. No checking or waiting for secondary indications, just close it down.

In which case it becomes a little more urgent, I hope you agree, as the Vmax, range and hover performance become seriously reduced... <img src="eek.gif" border="0">

[ 04 January 2002: Message edited by: ShyTorque ]</p>

[helmet fire]

Devil 49: I have to agree with Shy Torque. It depends on the flight manual.

But to my way of thinking, a chip light can hardly be compared to a sick passenger or weather diversion. Neither of these is an indication of possible catastrophic failure. It comes down to how willing you are to bet your life that the indication is minor. I dont bet my life, no matter how good the odds are. I throw the PAN out if there are no secondaries because they may appear on the way down when I am too busy handling the secondaries/failure to remember ATC. Or it the failure may appear on short finals when I have no time to react. At least someone is alerted. Either way, I will have a long time on the ground to cancel the call.

By the way, doesn't PAN mean you do, or you might need assistance, whilst MAYDAY is in need of immediate assistance? Thus for a chip with no secondaries I call PAN: i.e. watch over me in case I dont land safely. For secondaries (except one engine in a twin) a MAYDAY: i.e. It's serious, I may have a catastrophic failure, so start getting the help organised.

[Thomas coupling]

Interestingly, the crash check list for the AS355 states that in the event of a chip light in the TRGB: "continue flight, avoid prolonged hovering"...
For some pilots, this leads them to believe that the 'experts' have identified this as a minor inconvenience and that there is apparently little to worry about!

To my knowledge, atleast 2 355's have crashed because the pilot has continued flight with a TRGB chip light. One of them was caused by the GB departing the airframe.
No-one knows why the chip light comes on in the TRGB, is it because of debris, or heat!!

More startling to me, is that after 25+ years of service, the 355 crash check pertaining to this malfunction has not changed!!! No-one seems to have queried it?? [Lemmings comes to mind]. My military experience taught me to question everything. 9 times out of 10 it made sense, but occasionally, just ocassionally, something like this pops up and further research is required.
I changed our procedure, 7 years ago, to read:
In the event of a chip light from the TRGB, land ASAP.

[rotorque]

Too Cloudy,

I am very interested in having one of those supplements. I had better ask the obvious though, do you have LTS 750 donks? If so we should chat.

Helmut Fire,

You make a good point about the training aspect, I don't believe that any of the other drivers feel that they would roll up the machine in the example, more so they feel that the 'risk' of rolling up the machine (over torque maybe more likely ??)is higher than the risk of catastrophic failure. This may be due to the fact that some of the guys use to fly B222's (same engines) that would light up the panel with erroneous chip lights on a regular basis.

At the time I was listening to all comments with a vested interest, and the conclusion it seems is in line with most other people - "Depends on the circustances".

A good topic.

[ 10 January 2002: Message edited by: rotorque ]</p>

[BuzzLightyear]

I agree that for the warning MAYDAY would probably be a bit too much, but as has been pointed out if you call PAN at least we know that you may have a problem. In our environment even the use of the technical problem declaration would be better than not saying anything at all. We on the ground are guided by you, the pilot, in these situations. If you don't declare it, I can't really start to put the safeguards in place SHOULD it go badly wrong. We would rather alert people to a POTENTIAL problem than not say anything. It costs nothing to alert the emergency services and then cancel it, in terms of loss of life, should it go wrong, the penalty for not saying anything is significantly higher in the harsh environment that we work in.
There have been several instances where someone has not said anything about a problem, however minor they feel it is, which has escalated and they have not had time to make the call to us for help. I, believe it or not, as a controller have a vested interest in seeing you back safely, I do not want to have to go home at night having had one of "my" aircraft crash due to a problem I was not aware of. I am not hard enough to say "He didn't tell me something was wrong, so I don't care what happens". Make the call, we don't get angry if it all ends happily......

[helmet fire]

Rotortorque, I hear what you are saying - fair enough. A thought though: I think the concept of risk is often missunderstood, and if you view risk from a slightly different perspective than the way you have used the word above, I am sure we will find common ground. Risk equals consequence X frequency (according to Prof James Reason - the safety model guy). Applying that to a tail rotor gearbox chip: the frequency of a serious chip may be very low, but the consequence of such a chip is catastrophic failure and possible earthward plummeting. Therefore, in fact, the "risk" indicated by a tail rotor chip light cannot be said to be small.

Examining the risk of overtorque on a OEI landing to a suitable strip, the frequency would remain low (with appropriately trained crew it should be very unlikely) and the consequence (mechanical damage or inspection) would remain low because the pax are OK. Therefore frequency and consequence are low, thus risk must be low.

Hope that helps.

On to the LTS, it is a "cry wolf" syndrome that you speak of. Many spurious chips eventually lead to a perception that the risk is somehow reduced. But which one is a real chip? Which one do you bet your life on being spurious? Now that the LTS engines have had quite significant upgrades, spurious chips are much less frequent, and I think that the old feeling toward LTS chips should be put to bed. Your thoughts?

<img src="cool.gif" border="0">

[Variable Load]

Buzz

Perhaps I can try and explain why N Sea pilots working out of Aberdeen are reluctant to say anything? It's to do with what is considered (rightly in my opinion!) to be an overzealous reaction by the fire crews in Aberdeen.

Why are the fire services put on full alert even with a "technical diversion" when no Pan or Mayday is issued. By not raising at least a Pan the crew are stating that they do not consider the aircraft to be in any danger whatsoever, yet they will still be met by three or four fire trucks racing around with blue lights flashing and sirens blaring. All good fun for the fire crews I'm sure! What's even worse is that no matter what you tell the fire chief over the radio he'll insist on "escorting" you to the apron.

I don't believe the major issue is press coverage (although it always seems to get there - helped by bored fire crews it is rumoured!), it's more to do with the over the top reaction that results.

Is there any way the rules can be changed so that genuine emergencies (Pan/Mayday or if requested by the crew) are met with an appropriate response. But if I return because of an autopilot failure, or my undercarriage won't retract but is down, or I get some other minor defect that is not allowed in the aircraft Minimum Equipment List the all I want to do is land and taxy to the apron without fuss.

Any chance common sense can prevail and allow a rule change?

Perhaps an answer to the specific issue you raised at the start with regard to the chip warning was hidden in one of Lu's responses. Whan a newly overhauled gearbox is fitted, you will probably get a number of nuisance chip warnings being caused purely by build debris as the gears, etc all bed in. If the aircraft did have a "new" gearbox and there had been a recent history of chip warnings then I too would not have said anything but just turned the aircraft around!

[Too Cloudy]

Rotorque,
The engines on the Bk117 were 650's!
The Westpac Rescue service in Sydney, have the supplement. I also believe, but not 100% sure, that it has been incorporated in their Ops Manual.
Try the Chief Pilot on (02) 9 311 3499.

[rotorque]

Too Cloudy,

Thanks mate, I will give John a call.

Helmet Fire,

I hear ya. I was talking with coleagues today about this topic, what would the judge say? "You continued flight with the engine (it was an engine chip indication) chip light on and the engine let go causing an Ng blade to go through the second engine failing it also. How do you justify this".
Actually you can't. But as you mention about the LTS, the engine is now a very reliable powerplant. The supplement mentioned by 'Too Cloudy' adds credibility to this fact. We are now legally allowed to see if it is a 'wolf' or not.

Using yor risk assesment, as Nick Lappos has mentioned, the occurance of a catastrophic failure with a chip light is low yet the erroneus chip ellumination problems on the LTS remain high (ours anyway). This is, in essence, 'Risk Managment'. We as pilots deal with this every day.

As mentioned, there were several opinions on this particular occurence, and was one I was 'fortunate' enough to experience early on in my twin career. It brought out exactly the same comments/thoughts that you have mentioned plus others. I personally feel that an OEI landing is really just a formality and to date our Flight Manual states that we must shut down the engine and not restart it. My actions were already dictated to me from the beginning and I really didn't have a choice legally. You probably noticed, I failed to mention whether I did restart the donk or not, it makes the chat more interesting !!

Theoretically then, you can legally shut down the engine, roll up the machine OEI and stand in front of the judge with a righteous shrug of the shoulders and a sheepish grin on your face. <img src="wink.gif" border="0">

[U R NumberOne]

VL - hopefully common sense has prevailed!

With reference to the Fire Service - not only does it create reluctance with aircrew to declare something, but it can make the controller reluctant to make a call out (particularly if you have been berated on the RT by a pilot for their presence).

So a few months ago I had some discussions with them and the local operators to tone down the response, i.e. following the aircraft when not essential. As a result we now have a procedure in place where the vehicles will still turn out to their standby point but unless considered necessary by the Officer in charge, ATC or the pilot, will not follow the aircraft. As this has only been in place since October there probably hasn't been much time to establish the effectiveness but I hope this is a step in the right direction to prevent problems being mis-called.

[coalface]

The significance of a chip light varies depending on the system in question. For example, if I was in a single engine aircraft with an Allison C series engine and I had an engine chip light, I would declare a pan, carry out a good lookout for wires etc and land in the nearest suitable field (preferably next to a nice looking pub). These engines are operating at very high compressor speeds (&gt; 50,000rpm) and can go BANG quite suddenly in my experience.

If I was in a Makilla fitted twin engine aircraft (AS332L), of which only certain variants have engine chip lights, I would continue to my destination or return to a place with suitable maintenance facilities. I would not declare an emergency unless other symptoms were present (The flight manual says “continue flight&#8221).

By far the largest number of chip lights are caused by the build up of metalic dust on the detector over a period of time. In the case of new gearboxes, quite often a small piece of swarf from the manufacturing process can trigger a chip light. Again, this can be considered a “normal” event. I am not aware of any catastrophic failure of a system which was preceded by a chip light which would have given the pilot time to carry out a controlled landing before the situation became hazardous. I would like to hear from anyone who knows differently.

At the end of the day, one has to rely on the Flight Manual instructions. Most Eurocopter Flight Manuals now include definitions of required actions which include “Land/Ditch Immediately” (self explanatory), “Land as soon as possible” (land at the nearest available aerodrome) and “Land as soon as practicable” (extended flight not recommended).

As to the ATC situation; in Aberdeen (UK) North Sea operations we have a series of reasons for an unscheduled return to base stretching from “MAYDAY” which obviously causes all the stops to be pulled out, reducing to a return due to “Company” reasons which could mean a technical failure which does not hazard the aircraft but reduces the operational capability of the aircraft below that required for the flight. This system was introduced after a number of aircraft found themselves meeting a full complement of fire trucks after minor tech problems, one of which was a RNAV failure. This obviously gives the crew a problem having already told the passengers of the true reason for the return. These events were usually followed up by a wholly inaccurate report of “Major Air Drama with North Sea Copter” in the local paper. With agreement of ATC, we came up with the “Company requirement” to return if an aircraft suffered a failure for which the crew did not want any special ATC or RFF treatment. This would probably include an event with a “Land as soon as practicable” requirement.

[ 07 January 2002: Message edited by: coalface ]</p>

[Lu Zuckerman]

To: coalface

“I am not aware of any catastrophic failure of a system which was preceded by a chip light which would have given the pilot time to carry out a controlled landing before the situation became hazardous. I would like to hear from anyone who knows differently”.


I would suggest you read my post on page 2 of this thread. It is number 2 from the top.

I am not sure if the BV 107 that crashed from a seized transmission over the North Sea had a chip light or if it was just a catastrophic failure caused by a design defect with no warning provided.

[sling load]

Hey Lu,
I think that tandem that crashed in the north sea was a BV 234, I don't recall a BV 107 crashing in the north sea. Is there any details of that incident?

[coalface]

To Lu Z.

You make my point exactly. The light coming on a few seconds before the failure made no difference to what the pilot did.

As far as i can remember, the BV234 which broke up over the North Sea off the Shetland isles did not have a chip warning before the failure.

[Capn Notarious]

Are chip detectors usually only associated with tailrotor gearboxes. What systems exist to moniter the lubrication oil and the stages of the turbine.
Do any engineers have access to pictures of the insides of turbines/dissasembled gearboxes.
Could pictures be posted on the Rotorheads forum?