DA42 double engine failure
The alternators are 28V DC 60 Amp, that would seem to be enough.
In normal flight with everything turning and burning the load is app. 10 amps each.
When you cycle the gear this increases to about 28 amps each, therefore the gear motor draws about 30 amps.
The bus voltage drops from 28.5V to about 28.3V upon moving the gear lever.
The way I understand it; the ECU's are sensitive to a voltage drop over the bus.
With a low battery ( not sufficiently charged after a GPU start) that voltage drop could cause the ECU's to shut down, apparently what happened here.
I would have to check the maintenance manual to see how the GPU plug is wired, I have a suspicion that it bypasses the battery and the pilots in question simply did not allow enough time to charge the battery, even with both engines running on the ground.
BTW, the gear does not automatically come down with an electrical failure, over time it will slowly sag as the electric hydraulic pump is no longer able to keep the pressure @ 1600PSI. This could take a very long time though.
Here is the next scenario;
Dual alternator failure in flight, if you shut down half the G1000 system and all the exterior lights you have app. 45 min to find an airport since the ECU's need battery power to run the engines. In sight of the airport it would not be wise to lower the gear using the normal system. Considering the above mentioned article that could apparently lead to instantaneous dual engine shut down and feather. Trick would be to use the emergency extension (free fall) Need to check the POH to see if that is mentioned.
Plastic fantastic seems to have an Achilles heel, no different from other aircraft then.........
In normal flight with everything turning and burning the load is app. 10 amps each.
When you cycle the gear this increases to about 28 amps each, therefore the gear motor draws about 30 amps.
The bus voltage drops from 28.5V to about 28.3V upon moving the gear lever.
The way I understand it; the ECU's are sensitive to a voltage drop over the bus.
With a low battery ( not sufficiently charged after a GPU start) that voltage drop could cause the ECU's to shut down, apparently what happened here.
I would have to check the maintenance manual to see how the GPU plug is wired, I have a suspicion that it bypasses the battery and the pilots in question simply did not allow enough time to charge the battery, even with both engines running on the ground.
Diamond says that retracting the gear placed a load on the electrical supply from the engine-driven alternators that caused a temporary voltage drop that could not be covered by the flat battery, and the accident has shown the engine control unit to be intolerant of transient electrical fluctuations
Diamond dismisses these claims and argues the control unit supplied by TAE should have been able to accept a 50 millisecond transient, but it started to reset after 1.7 milliseconds, and during the engine control unit reset the propeller system sensed the power loss and auto-feathered.
BTW, the gear does not automatically come down with an electrical failure, over time it will slowly sag as the electric hydraulic pump is no longer able to keep the pressure @ 1600PSI. This could take a very long time though.
Here is the next scenario;
Dual alternator failure in flight, if you shut down half the G1000 system and all the exterior lights you have app. 45 min to find an airport since the ECU's need battery power to run the engines. In sight of the airport it would not be wise to lower the gear using the normal system. Considering the above mentioned article that could apparently lead to instantaneous dual engine shut down and feather. Trick would be to use the emergency extension (free fall) Need to check the POH to see if that is mentioned.
Plastic fantastic seems to have an Achilles heel, no different from other aircraft then.........
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The 1.7 milliseconds is the one which scares me. The DA-40 I fly presumably has the same FADECs with the same problems. What's the time required for a relay (or two relays in series) to switch? Because on the DA-40 you've got the ECU backup battery, but it requires at least one relay to switch (maybe even two, I do not have the POH to hand at this moment) to activate after a main bus failure.
Although I'd be very surprised if extending this time to the 50 milliseconds mentioned would help in the case we're discussing here. AFAIK, the gear doesn't come up in less than 50 milliseconds...
B2N2, does the gear motor also draw 30 amps when *lowering* the gear?
Although I'd be very surprised if extending this time to the 50 milliseconds mentioned would help in the case we're discussing here. AFAIK, the gear doesn't come up in less than 50 milliseconds...
B2N2, does the gear motor also draw 30 amps when *lowering* the gear?
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Originally Posted by BackPacker
The DA-40 I fly presumably has the same FADECs with the same problems. What's the time required for a relay (or two relays in series) to switch? Because on the DA-40 you've got the ECU backup battery, but it requires at least one relay to switch (maybe even two, I do not have the POH to hand at this moment) to activate after a main bus failure.
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On those specs you could easily hook up an emergency battery system that employs one diode and one sealed battery for each ECU that will maintain minimum voltage/current for each of the four ECUs for over an hour (if that's how long you want to spend playing with the gear/waiting for battery to charge), for a total weight penalty less than 2kg and a cost less than £50. Certification of course would be a different question.
What a ludicrous design. Adding documentation procedures is not a human factors solution, it's a recipe for more accidents. If it's the preferred solution to prohibit starting both engines on ground power, then the design itself should prohibit starting both engines on ground power...
What a ludicrous design. Adding documentation procedures is not a human factors solution, it's a recipe for more accidents. If it's the preferred solution to prohibit starting both engines on ground power, then the design itself should prohibit starting both engines on ground power...
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soay, that's good to know... HOWEVER. I have here an article written for my clubs newsletter which deals with exactly the same problem. I just remembered reading about that, so I looked it up. It's a bit long (and in Dutch), so I'll try to summarize it here.
"
If you switch off the Electric Master while the engine is running idle (on the ground) the engine will halt, despite the fact that it should continue running on the ECU B Backup Battery. The articles analysis is that the switch to ECU B does happen as designed, however, the Thielert is a high-compression engine and at IDLE power only runs at 890 RPM or so. With this rotation speed there is insufficient impulse-moment to maintain rotation while ECU B is taking over. Because of that, the engine halts. Apparently, the engine needs at least 1300 RPM to maintain its momentum throughtout the process of ECU B taking over.
If you switch on the Electric Master again while the engine is running idle, the reboot of ECU A plus its takeover from ECU B takes even more time. Again, experimenting showed that at least 1300 RPM is required for a smooth takeover.
Conclusions:
- In the air, switching off, or switching off/on of the Electric Master, the engine will continue running due to the windmilling effect, even at idle power.
- On the ground, at least 1300 RPM is required for the engine to keep on running when the Electric Master is switched off, or off/on.
"
This analysis was published in July 2006, and although its conclusions may be right, with what I've read on this forum, the whole issue might not be sufficient impulse-moment, but ECUs that are too sensitive to power spikes.
How all this applies to the DA-42 that this thread is about, I don't know, since I assume that its engines were running at full speed, since they were just after take-off, raising the gear. But I do have that nasty feeling that there is a link somewhere.
Glad the DA-40 has "gear down and welded" though.
"
If you switch off the Electric Master while the engine is running idle (on the ground) the engine will halt, despite the fact that it should continue running on the ECU B Backup Battery. The articles analysis is that the switch to ECU B does happen as designed, however, the Thielert is a high-compression engine and at IDLE power only runs at 890 RPM or so. With this rotation speed there is insufficient impulse-moment to maintain rotation while ECU B is taking over. Because of that, the engine halts. Apparently, the engine needs at least 1300 RPM to maintain its momentum throughtout the process of ECU B taking over.
If you switch on the Electric Master again while the engine is running idle, the reboot of ECU A plus its takeover from ECU B takes even more time. Again, experimenting showed that at least 1300 RPM is required for a smooth takeover.
Conclusions:
- In the air, switching off, or switching off/on of the Electric Master, the engine will continue running due to the windmilling effect, even at idle power.
- On the ground, at least 1300 RPM is required for the engine to keep on running when the Electric Master is switched off, or off/on.
"
This analysis was published in July 2006, and although its conclusions may be right, with what I've read on this forum, the whole issue might not be sufficient impulse-moment, but ECUs that are too sensitive to power spikes.
How all this applies to the DA-42 that this thread is about, I don't know, since I assume that its engines were running at full speed, since they were just after take-off, raising the gear. But I do have that nasty feeling that there is a link somewhere.
Glad the DA-40 has "gear down and welded" though.
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BackPacker, part of the pre-takeoff checks for a DA40 is to switch to ECU B, then back to auto, with the power at idle. This has never caused more than a slight hiccup, in my experience. Power was certainly at idle when I switched off the electric master, and the engine kept running, so I don't know why your club reported differently in their newsletter.
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Same here. Switching from ECU Auto to B causes a slight hiccup. That's all. I've never switched the electric master off with the engine running. I guess that's something to experiment with next time I lay my hands on her.
The reason for the report was that in the early days we had the DA-40, people were still used to Pipers, and switched (or tried to, at least) the engine off with the electric master (key) instead of the engine master (I guess in absence of a mixture control). Obviously that's not what the POH and the checklist say is the right procedure but the unexpected result was what prompted the investigation. Or at least, that's what it said in the article. I wasn't flying the DA-40 at that time.
The reason for the report was that in the early days we had the DA-40, people were still used to Pipers, and switched (or tried to, at least) the engine off with the electric master (key) instead of the engine master (I guess in absence of a mixture control). Obviously that's not what the POH and the checklist say is the right procedure but the unexpected result was what prompted the investigation. Or at least, that's what it said in the article. I wasn't flying the DA-40 at that time.
What a ludicrous design. Adding documentation procedures is not a human factors solution, it's a recipe for more accidents. If it's the preferred solution to prohibit starting both engines on ground power, then the design itself should prohibit starting both engines on ground power...
Anytime something out of the usual occurs; refer to the POH.
That's what it's there for, that's why it should be within reach of the pilot in the cockpit, not in the luggage compartment.
It is not that hard to follow instructions, section 4B7 DOES read " start one engine only,
here is the copy & paste of the online manual
http://www.diamond-air.at/fileadmin/...4-complete.pdf
' 10. Circuit breakers . . . . . . . . . . . . . . . . . . . . . . . check all in / as required
' 11. Idle RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . check, 900 ±20 RPM
' 12. External Power . . . . . . . . . . . . . . . . . . . . . . . disconnect
' 13. Opposite engine . . . . . . . . . . . . . . . . . . . . . . Start with normal procedure
' 14.Warm up . . . . . . . . . . . . . . . . . . . . . . . . . . . . IDLE for 2 minutes /
thereafter 1400 RPM
' 11. Idle RPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . check, 900 ±20 RPM
' 12. External Power . . . . . . . . . . . . . . . . . . . . . . . disconnect
' 13. Opposite engine . . . . . . . . . . . . . . . . . . . . . . Start with normal procedure
' 14.Warm up . . . . . . . . . . . . . . . . . . . . . . . . . . . . IDLE for 2 minutes /
thereafter 1400 RPM
On the DA-42 the engines continue to run if you shut off the master switch on the ground.
According to the above mentioned article the ECU's are sensitive to under voltage situations on the electrical bus.
With a battery that is insufficiently charged an under voltage can oocur upon cycling the gear on any other high draw item.
Last edited by B2N2; 28th Apr 2007 at 14:15.
As an after thought; a lot of airplanes have design features that make you go Hmmm.....
> Older models Cessna 172, hard fuel lines with a rubber bend going through the A-pillar on the pilot and pass side. Notorious for drying out, cracking and leaking. Several fires (in flight) have occurred as a result of the cockpit lighting switch (half way the A-pillar) shorting out.
> Piper Cherokee Six, 4 fuel tanks of 17 gallons each. Fuel flow on T/O is app. 30 gall./hr. Surely makes for a lot of switching in a high work load environment if you take off with less then full tanks.
> Piper Cherokee/Warrior series, nice fuel selector in an awkward place, easy to turn to an intermediate position or even OFF because of the lack of a stop.
> Any airplane with only one door on the wrong (= passenger) side.
> Piper AeroStar, loads of people taxi with the door open, waiting to loose an arm.
> any aircraft with a "wet-wing" fuel system, wing damage= tank damage= fuel leak= fire...
> Vacuum pumps that can get damaged if you turn the propeller against the normal direction of rotation, this will lead to early failure. Don't read about that in a POH.
> Dry vacuum pumps period, who ever came up with those needs to be shot...lubrication by self destruction is what it's called. They "recommend"
replacement after 500 hrs.
I could go on for hours....
Point being, aircraft are inherently dangerous, proper training and application of common sense can reduce the chances of an accident or incident.
End of rant...I'll get my coat.
> Older models Cessna 172, hard fuel lines with a rubber bend going through the A-pillar on the pilot and pass side. Notorious for drying out, cracking and leaking. Several fires (in flight) have occurred as a result of the cockpit lighting switch (half way the A-pillar) shorting out.
> Piper Cherokee Six, 4 fuel tanks of 17 gallons each. Fuel flow on T/O is app. 30 gall./hr. Surely makes for a lot of switching in a high work load environment if you take off with less then full tanks.
> Piper Cherokee/Warrior series, nice fuel selector in an awkward place, easy to turn to an intermediate position or even OFF because of the lack of a stop.
> Any airplane with only one door on the wrong (= passenger) side.
> Piper AeroStar, loads of people taxi with the door open, waiting to loose an arm.
> any aircraft with a "wet-wing" fuel system, wing damage= tank damage= fuel leak= fire...
> Vacuum pumps that can get damaged if you turn the propeller against the normal direction of rotation, this will lead to early failure. Don't read about that in a POH.
> Dry vacuum pumps period, who ever came up with those needs to be shot...lubrication by self destruction is what it's called. They "recommend"
replacement after 500 hrs.
I could go on for hours....
Point being, aircraft are inherently dangerous, proper training and application of common sense can reduce the chances of an accident or incident.
End of rant...I'll get my coat.
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As a very long time aircraft driver having driven 'biggies' as a job for many years but 'seen the light', but first time user to this forum I will say:
I am somewhat alarmed by the attitude of B2N2 on the 'horror story' of the double engine failure on a DA42 as he seems to be connected in some way with Diamond Aircraft or a major operator or investor in these aircraft in the good old US of A. I do hope it does not reflect the attitude of his principles.
I am merely a poor sod eagerly waiting, but now rather alarmed, new owner awaiting delivery of a DA42.
Without wanting to get into 'geekish techno arguments' it would seem to me that it is not an unreasonable expectation that if you take off having started both engines on the GPU, which is quite normal operating procedure on every aircraft I have ever flown, and retract the undercarriage you should not expect both engines to stop! That the accident is in some part due to the crew not adhering to the checklist seems to me not to be a 'robust' solution to a clear design failure; and that Diamond have issued an advisory to start in accordance with the checklist does not solve the problem either. Hopefully it will just ensure this particualr type of incident does not happen again. It does not solve the problem of a major electrical problem stopping both engines!
I think that Diamond and Thielert should stop squabbiling about what is to be done, or more likely who is to pay, and get on and do a proper fix ASAP before someone gets killed. Clearly there is an acceptance by both parties that there is a problem despite what has been suggested by some on this forum.
The fact that EASA have said fix it pronto or we will issue a directive speaks volumes about this poor design.
Despite all of the above I do believe this aircraft is the greatest thing since sliced bread. I have little doubt that this surprising design failure will be fixed either by EASA or those involved soon and on my aircraft the engines will run after a total DC collapse - or some motor starting up or burning out somewhere and dropping busbar voltage for 1.7 milliseconds! One blessing I suppose is with it's heritage the DA42 should glide quite well!
I never thought I would be grateful to a 'bunch of bureaucrats' for knocking heads together; and it is alarming that they may have to!
I am somewhat alarmed by the attitude of B2N2 on the 'horror story' of the double engine failure on a DA42 as he seems to be connected in some way with Diamond Aircraft or a major operator or investor in these aircraft in the good old US of A. I do hope it does not reflect the attitude of his principles.
I am merely a poor sod eagerly waiting, but now rather alarmed, new owner awaiting delivery of a DA42.
Without wanting to get into 'geekish techno arguments' it would seem to me that it is not an unreasonable expectation that if you take off having started both engines on the GPU, which is quite normal operating procedure on every aircraft I have ever flown, and retract the undercarriage you should not expect both engines to stop! That the accident is in some part due to the crew not adhering to the checklist seems to me not to be a 'robust' solution to a clear design failure; and that Diamond have issued an advisory to start in accordance with the checklist does not solve the problem either. Hopefully it will just ensure this particualr type of incident does not happen again. It does not solve the problem of a major electrical problem stopping both engines!
I think that Diamond and Thielert should stop squabbiling about what is to be done, or more likely who is to pay, and get on and do a proper fix ASAP before someone gets killed. Clearly there is an acceptance by both parties that there is a problem despite what has been suggested by some on this forum.
The fact that EASA have said fix it pronto or we will issue a directive speaks volumes about this poor design.
Despite all of the above I do believe this aircraft is the greatest thing since sliced bread. I have little doubt that this surprising design failure will be fixed either by EASA or those involved soon and on my aircraft the engines will run after a total DC collapse - or some motor starting up or burning out somewhere and dropping busbar voltage for 1.7 milliseconds! One blessing I suppose is with it's heritage the DA42 should glide quite well!
I never thought I would be grateful to a 'bunch of bureaucrats' for knocking heads together; and it is alarming that they may have to!
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72856, welcome to this forum. And soon: welcome to the club of Diamond owners/operators/pilots.
I have flown the clubs DA-40 TDI for about four months and I really like the plane. But we all need to remember that this is the first application of the Thielert diesel in a certificated airplane, and as such, the pilot community in general needs to build experience in handling this kind of engine. Some of us use this forum for exactly that. And eventually, I hope, some of the experience and knowledge that we gained will filter its way through into formal ab-initio pilot training. (Aircraft Technical, for starters.)
One main difference of the Thielert, as compared to the majority of the light aircraft fleet most of us come from, is a total reliance on an electric system, to power the ECUs. Now we can argue about whether this total reliance is good or bad (and we actually do, here on this forum) but at the end of the day we'll just have to accept that a small aircraft will not have the double, triple or more redundancy built-in as the big iron do. So it is very important to learn the POH and know what weaknesses the aircraft has, and what procedures that are out of the ordinary. I, for one, really like the fact that there is no mixture, and more importantly, carb heat to get wrong. (How many pilots have been killed because of carb ice?)
Not discussing an apparent safety issue, as far as I'm concerned, is a greater sin than the safety issue itself. Even if some people voice their opinion a bit loudly. But this whole discussion prompted me to review parts of the DA-40 POH again, to see to what extent the aircraft I fly would be vulnerable to the same thing. I learned something from that and I have a question or two that I will get answered by a bit of experimenting (on the ground) next time I get my hands on the plane.
I suggest you do the same. As soon as your beauty arrives, spend some time experimenting with the ECUs. Particularly try to simulate (e.g. by pulling the circuit breakers) the situation where you have a dual alternator + battery failure and the ECUs need to take over from each other somehow.
The DA-40 is a great plane. The DA-42 should be even better. I really hope you're going to enjoy it!
I have flown the clubs DA-40 TDI for about four months and I really like the plane. But we all need to remember that this is the first application of the Thielert diesel in a certificated airplane, and as such, the pilot community in general needs to build experience in handling this kind of engine. Some of us use this forum for exactly that. And eventually, I hope, some of the experience and knowledge that we gained will filter its way through into formal ab-initio pilot training. (Aircraft Technical, for starters.)
One main difference of the Thielert, as compared to the majority of the light aircraft fleet most of us come from, is a total reliance on an electric system, to power the ECUs. Now we can argue about whether this total reliance is good or bad (and we actually do, here on this forum) but at the end of the day we'll just have to accept that a small aircraft will not have the double, triple or more redundancy built-in as the big iron do. So it is very important to learn the POH and know what weaknesses the aircraft has, and what procedures that are out of the ordinary. I, for one, really like the fact that there is no mixture, and more importantly, carb heat to get wrong. (How many pilots have been killed because of carb ice?)
Not discussing an apparent safety issue, as far as I'm concerned, is a greater sin than the safety issue itself. Even if some people voice their opinion a bit loudly. But this whole discussion prompted me to review parts of the DA-40 POH again, to see to what extent the aircraft I fly would be vulnerable to the same thing. I learned something from that and I have a question or two that I will get answered by a bit of experimenting (on the ground) next time I get my hands on the plane.
I suggest you do the same. As soon as your beauty arrives, spend some time experimenting with the ECUs. Particularly try to simulate (e.g. by pulling the circuit breakers) the situation where you have a dual alternator + battery failure and the ECUs need to take over from each other somehow.
The DA-40 is a great plane. The DA-42 should be even better. I really hope you're going to enjoy it!
Howdy 72865, welcome to Pprune.
As an Instructor ( not the operator) I fly Diamonds for a living, every day, all day (long days..
)
I was equally surprised by the double failure as many people are.
Good thing is that the source of the problem seems to be identified with (I'm sure) a fix on the way. It's not exactly a new airplane anymore with thousands of hours flown in Europe, Asia (China) and now the US.
It's not unusual for problems to surface after some time, you can check the AD list on any popular piston single/twin.
I am just somewhat cynical and sarcastic about blaming the tool and not the operator. They clearly went against the POH in this case.
That can get you into trouble in any airplane, not only the DA-42.
At the risk of sounding arrogant, it is my job to teach people how to operate this piece of machinery, it's not always that easy to convince people of doing it the right way.
However, you will receive outstanding ground school and flight instruction upon delivery of your airplane. I was trained by the Diamond Factory pilots in Canada.
I hope that also...
As an Instructor ( not the operator) I fly Diamonds for a living, every day, all day (long days..
)I was equally surprised by the double failure as many people are.
Good thing is that the source of the problem seems to be identified with (I'm sure) a fix on the way. It's not exactly a new airplane anymore with thousands of hours flown in Europe, Asia (China) and now the US.
It's not unusual for problems to surface after some time, you can check the AD list on any popular piston single/twin.
I am just somewhat cynical and sarcastic about blaming the tool and not the operator. They clearly went against the POH in this case.
That can get you into trouble in any airplane, not only the DA-42.
At the risk of sounding arrogant, it is my job to teach people how to operate this piece of machinery, it's not always that easy to convince people of doing it the right way.
However, you will receive outstanding ground school and flight instruction upon delivery of your airplane. I was trained by the Diamond Factory pilots in Canada.
I do hope it does not reflect the attitude of his principles
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Thanks for the welcome!
I don't expect I will be doing too many posts - not my scene. I was only prompted to do so by the suggestion that the blame largly lay in not adhering to a checklist.
Since I quit being an airline captain long ago I have owned a number of light aircraft - possible the 'heaviest' being a Cessna Golden Eagle and the 'lightest' a Grob 109.
By the way I flew into Schipol many times a long time ago as a very young captain for SABENA (RIP). A very hard way to build hours and earn a crust but you did get very good at doing an ILS doing eight short sectors a day.
I may stand corrected but on none of these aircraft, including 'heavy metal' airliners, did the engines stop if you had a major DC busbar failure. I do take your point that the Thielert engine is revolutionary and in fact it is what attracted me to the aircraft. I was about to buy a Piper Mirage. It has many advantages that you mention like ease of handling, and above all immunity from mishandling, so it is likely to reach it's TBO unlike a lot of conventional piston engines. However, I maintain that the engines should not stop with a major electrical problem, let alone a minor one! The way I was taught at Airline Flying School ARB lectures a very long time ago was that no major system should rely on another major system. They should be stand alone and not inter-dependant - most certainly the engines.
In fact Thielert, Diamond and EASA all agree with this in effect. The only argument seems to be who pays and whose reputation takes a knock. Theilert seem very determined it should not be them. Without knowing all the facts of the matter I would hesitate to aportion responsibility and liability. But I will say I started being sympathetic to the Diamond argument. Having learnt that the DA40 has a back up battery from this website I now lean to Thielert. If a battery backed up FADEC was available and fitted to the DA40 why did Diamond not specify it for the DA42? I expect it is very much six of one and half a dozen of the other though.
My concern is a proper fix is arrived at and the fix means the engines will not just run for one hour after a total electrical failure but for at least five hours - half the endurance of the aircraft so that when it all goes dark half way across the Bay of Bengal I can reasonably expect to reach the other side with the propellers still turning and not in glide mode!
I think the DA42 is a great aircraft with revolutionary engines and it was a 'marriage made in heaven'. I believe the owner of Diamond aircraft has said as much. It saddens me to see what seems to be rather undignified squabbiling now over who pays over such an important issue; if for no other reason than the resale value of my new toy! I can't imagine the fix will cost a mountain of money to two companies on such a roll.
I am confident there will be a fix very soon; and not just a 'read the checklist' missive from Diamond!
I have little doubt I will enjoy the new toy, particularly the running costs after a C421. It is certainly a 'drop dead gorgeous' looking piece of kit. It even has the same 'phallic nose' as the Golden Eagle, another gorgeous piece of kit. My Golden Eagle also had those wonderful tip tanks, and it made the most glorious noise - a whole lot better than a V12 Ferrari!
I don't expect I will be doing too many posts - not my scene. I was only prompted to do so by the suggestion that the blame largly lay in not adhering to a checklist.
Since I quit being an airline captain long ago I have owned a number of light aircraft - possible the 'heaviest' being a Cessna Golden Eagle and the 'lightest' a Grob 109.
By the way I flew into Schipol many times a long time ago as a very young captain for SABENA (RIP). A very hard way to build hours and earn a crust but you did get very good at doing an ILS doing eight short sectors a day.
I may stand corrected but on none of these aircraft, including 'heavy metal' airliners, did the engines stop if you had a major DC busbar failure. I do take your point that the Thielert engine is revolutionary and in fact it is what attracted me to the aircraft. I was about to buy a Piper Mirage. It has many advantages that you mention like ease of handling, and above all immunity from mishandling, so it is likely to reach it's TBO unlike a lot of conventional piston engines. However, I maintain that the engines should not stop with a major electrical problem, let alone a minor one! The way I was taught at Airline Flying School ARB lectures a very long time ago was that no major system should rely on another major system. They should be stand alone and not inter-dependant - most certainly the engines.
In fact Thielert, Diamond and EASA all agree with this in effect. The only argument seems to be who pays and whose reputation takes a knock. Theilert seem very determined it should not be them. Without knowing all the facts of the matter I would hesitate to aportion responsibility and liability. But I will say I started being sympathetic to the Diamond argument. Having learnt that the DA40 has a back up battery from this website I now lean to Thielert. If a battery backed up FADEC was available and fitted to the DA40 why did Diamond not specify it for the DA42? I expect it is very much six of one and half a dozen of the other though.
My concern is a proper fix is arrived at and the fix means the engines will not just run for one hour after a total electrical failure but for at least five hours - half the endurance of the aircraft so that when it all goes dark half way across the Bay of Bengal I can reasonably expect to reach the other side with the propellers still turning and not in glide mode!
I think the DA42 is a great aircraft with revolutionary engines and it was a 'marriage made in heaven'. I believe the owner of Diamond aircraft has said as much. It saddens me to see what seems to be rather undignified squabbiling now over who pays over such an important issue; if for no other reason than the resale value of my new toy! I can't imagine the fix will cost a mountain of money to two companies on such a roll.
I am confident there will be a fix very soon; and not just a 'read the checklist' missive from Diamond!
I have little doubt I will enjoy the new toy, particularly the running costs after a C421. It is certainly a 'drop dead gorgeous' looking piece of kit. It even has the same 'phallic nose' as the Golden Eagle, another gorgeous piece of kit. My Golden Eagle also had those wonderful tip tanks, and it made the most glorious noise - a whole lot better than a V12 Ferrari!
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The pilot broke the rules and paid for it. There's going to be hell about this - neither Thielert or Diamond will back down. A 1.7ms power transient should be tolerable - losing both engines because of it is ridiculous, as are the electrically dependent engines. I can just imagine the Thielert engineers saying 'Now, how do we create a weak link in the engine design?'
Eureka! Aircraft engines that need electricity to continue running
Now there's no doubt the DA42 is a great aircraft even after the abortive promotion specs, but this is ridiculous, and it's one thing I don't understand about flying and aircraft manufacturers in general - why don't they think of these things in the first place? With all the money they've spent you'd think someone would go 'What if this happens?'
Out of curiosity - are there any other commercial aviation powerplants that require electricity to continue running? Can't think of any offhand.
Eureka! Aircraft engines that need electricity to continue running
Now there's no doubt the DA42 is a great aircraft even after the abortive promotion specs, but this is ridiculous, and it's one thing I don't understand about flying and aircraft manufacturers in general - why don't they think of these things in the first place? With all the money they've spent you'd think someone would go 'What if this happens?'
Out of curiosity - are there any other commercial aviation powerplants that require electricity to continue running? Can't think of any offhand.
Last edited by Confabulous; 28th Apr 2007 at 23:16.
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My background is also big aeroplanes, although I am now associated with smaller ones whilst instructing in CRM/MCC. I know that ALL aeroplanes have potentially dangerous properties and that a properly written SOP (as in this case) correctly followed (as not here) will minimise the risk.
This incident has overtones of the British Midland B737-400 crash in the late 1980s - a design fault in the CFM 56 engine caused a blade failure but an incident was turned into an accident (with over 40 fatalities) because the crew did not follow the SOP. As crew it is our job to know the aeroplane, its characteristics, its drills and most important its shortcomings.
It's absolutely explicitly stated in the POH that you must not start the second engine from the GPU. This ensures that the battery has charged sufficiently to provide the necessary oomph to run the systems. It would be nice if the alternators produced enough juice to run everything, but they don't. However, there IS a procedure that mitigates the problem.
It's no worse than the fact that you can blow a Seneca engine apart by overboosting due to the fact that they are fitted with turbochargers without wastegates. The difference here is that, after a bit of a spat, Thielert and Diamond will get it sorted - but the Seneca still doesn't have wastegates after 20+ years.
The checklist on ANY aeroplane covers all sorts of actions which, if not followed correctly, can lead to disaster. Airline SOPs have to be written to take account of the fact that many turbine engines can flame out when anti-ice is switched on (CFM 56 and PT6 to name but two) but no-one wants the manufacturers head on a block, even though a friend of mine was killed by a double flameout on a PT6 powered Short 360.
No-one died here, lessons will be learned and the problem sorted. That's more than can be said for some aeroplanes.
Last edited by moggiee; 29th Apr 2007 at 01:29.
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Am I the only one who's puzzled by the POH?
You have flat batteries
You start one engine using ground power
You disconnect the ground power
You now have flat batteries being charged by one alternator
You get enough charge into the batteries to crank the other engine, that depletes the charge, you have flat batteries again.
You take off.
Who's to say that the charge in the batteries is now sufficient to maintain voltage under load?
What happens to the 45 minutes ECU endurance mentioned by B2N2 following electrical failure in this situation?
For years boats have had a very simple system with a separate engine starting battery arranged using a blocking diode so that it is not depleted by the domestic load. As Vedeneyev suggests it's not difficult to set up a similar arrangement to provide a fully charged ECU battery permanently on-line.
I don't buy the arguments of moggiee et al. For years aircraft crashed because non-return valves were manufactured so that they could be inserted either way round. Writing documentation that said they had to be inserted the right way round didn't fix it. Making it mechanically impossible by having differing threads on each end did. If you follow the argument to its logical conclusion you wouldn't have squat switches or GPWS either because if the procedures were followed correctly the need for them would never arise.
You have flat batteries
You start one engine using ground power
You disconnect the ground power
You now have flat batteries being charged by one alternator
You get enough charge into the batteries to crank the other engine, that depletes the charge, you have flat batteries again.
You take off.
Who's to say that the charge in the batteries is now sufficient to maintain voltage under load?
What happens to the 45 minutes ECU endurance mentioned by B2N2 following electrical failure in this situation?
For years boats have had a very simple system with a separate engine starting battery arranged using a blocking diode so that it is not depleted by the domestic load. As Vedeneyev suggests it's not difficult to set up a similar arrangement to provide a fully charged ECU battery permanently on-line.
I don't buy the arguments of moggiee et al. For years aircraft crashed because non-return valves were manufactured so that they could be inserted either way round. Writing documentation that said they had to be inserted the right way round didn't fix it. Making it mechanically impossible by having differing threads on each end did. If you follow the argument to its logical conclusion you wouldn't have squat switches or GPWS either because if the procedures were followed correctly the need for them would never arise.
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Stepping back a bit, I think the problem is that a lot of people are used to conventional engines and their separate mags. They are "safe" to fly on a flat battery, just so long as you can somehow get the engine started. Loads of people have done this, getting somebody to hand crank or start with a GPU.
Checklist or no checklist, I don't think people expect to have this rather odd failure mode. Also, a lot of pilots are used to flying without checklists - they jump in and fly. It's not right but it's an old tradition throughout GA. On an old C152 you get away with it. But people who rent these nice new machines will have to get their head in gear, and if the owner does even half decent vetting this is going to reduce the number of eligible pilots!
For some reason it's difficult to get a "two batteries with diodes" thing certified. It's such an obvious solution to electrical power issues but I know people have tried in (in the USA with a 337, usually) and gave up. It would be a great solution to a comms failure: feed the radio(s) via diodes and have a 2nd battery somewhere. 2 radios won't both fail together. Instead, one has to carry a handheld ICOM...
Checklist or no checklist, I don't think people expect to have this rather odd failure mode. Also, a lot of pilots are used to flying without checklists - they jump in and fly. It's not right but it's an old tradition throughout GA. On an old C152 you get away with it. But people who rent these nice new machines will have to get their head in gear, and if the owner does even half decent vetting this is going to reduce the number of eligible pilots!
For some reason it's difficult to get a "two batteries with diodes" thing certified. It's such an obvious solution to electrical power issues but I know people have tried in (in the USA with a 337, usually) and gave up. It would be a great solution to a comms failure: feed the radio(s) via diodes and have a 2nd battery somewhere. 2 radios won't both fail together. Instead, one has to carry a handheld ICOM...
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Despite all the previous posts about following the POH and SOP (which are technically correct, mind you), I still tend to lean towards blaming the aircraft, not the crew.
Sure, if you have flown big iron for all of your life, you know that there's a checklist or SOP for every possible contingency. And since most of these aircraft are multi-crew anyway, one pilot can fly while the other thumbs through the POH to see if a certain checklist matches the abnormal situation that has arisen.
But if you come from a smaill airplane background, single pilot, the situation is a bit different. Sure, there might be a checklist in the POH, but we all know that nobody uses the checklist from the actual POH itself. Instead, you use an abbreviated checklist because the actual POH is too big to have on your lap at all times. First question: did this abbreviated checklist contain a separate item "starting with ground power" or at least a warning that the "starting with ground power" procedure is significantly different from "starting with battery power", and that reference needed to be made to the actual POH? I just checked the three POHs I have here, and the corresponding (owner/operator-issued) abbreviated checklists. I found that both the DA-40 (!!!) and the Robin do not have "GPU-assisted start" checklists in the actual POH (let alone in the abbreviated checklists I use), and while the Piper Warrior has such a procedure in the POH, that procedure gets no mention into the two abbreviated checklists I have here (from two different operators).
The second factor is that if the crew (or single pilot, let's not rule that out) even knew that such a procedure existed in the POH, did he remember at the correct time? We don't know what kind of flight it is, whether he had (potentially nervous) passengers around and such. But we can assume that he was under a little more stress than usual. After all, if you find yourself preflighting an aircraft and discovering the battery is flat, you may have to do all sorts of things that you've never had to do before: find a GPU and somebody knowledgeable and willing to assist you with it (and will that person have specific experience with the DA-42, or only with more traditional twins & singles?). Find the GPU receptacle, possibly discovering that the standard plugs do not fit. The stress of having somebody walking very close to the fuselage with the engines running. And the stress of all your mates looking at you at the clubhouse, because this is something out of the ordinary and that attracts attention by default. Now you can argue that one of the things a pilot needs to do is manage stress, and that all this should not impact your performance, but you have to admit that this may just be a factor in not starting to read the POH, looking for the appropriate checklist.
And the third factor is that the POH may not be of much help anyway. I just read through the Warrior POH with regards to the external power startup (admittedly, first time I ever read that part, didn't even know it was in), and basically it comes down to this:
- All electrics off
- Connect GPU
- Normal start according to normal start checklist
- Lowest revs as possible
- Disconnect GPU
And that's exactly what I would have expected it to say. The GPU is connected, replaces the function of the main battery so you can do a normal start, and you've got to be careful while somebody removes the GPU. I even can understand that with a twin the procedure would be to connect the GPU on the left hand side, then start the right hand side, disconnect, start the left hand side. But I would read that as a safety issue with regards to the person disconnecting the GPU, not something that would assure a sufficiently charged battery to raise the gear (far later into the flight). So if I were to find out that after starting the first engine and disconnecting the GPU, the second engine wouldn't start? I would hook up the GPU again and start the second engine.
As I said before, yes, formally we've got to use the POH and SOP with everything we do. But in reality, things are not that simple, for starters because the POH itself is way too bulky to keep on your lap throughout the flight. So we use abbreviated checklists, improvise when necessary, do things from memory and even forget things from time to time. The aircraft should be designed so that this does not lead to a potentially deadly incident, which EFATO clearly is. So if it is possible to get into a situation where you have both engines running but a depleted main battery (either though an improperly executed GPU procedure or in the situation where the battery just had enough juice to start two engines but then gave up the ghost) then the aircraft should be designed so that at the very least, when you raise the gear, the engines keep on running.
The DA-40 has ECU backup batteries which cannot be depleted except in case they run the ECU. As far as I'm concerned, that's a good start. Without something like this, it's an accident which can happen again, despite the procedure in the POH.
Sure, if you have flown big iron for all of your life, you know that there's a checklist or SOP for every possible contingency. And since most of these aircraft are multi-crew anyway, one pilot can fly while the other thumbs through the POH to see if a certain checklist matches the abnormal situation that has arisen.
But if you come from a smaill airplane background, single pilot, the situation is a bit different. Sure, there might be a checklist in the POH, but we all know that nobody uses the checklist from the actual POH itself. Instead, you use an abbreviated checklist because the actual POH is too big to have on your lap at all times. First question: did this abbreviated checklist contain a separate item "starting with ground power" or at least a warning that the "starting with ground power" procedure is significantly different from "starting with battery power", and that reference needed to be made to the actual POH? I just checked the three POHs I have here, and the corresponding (owner/operator-issued) abbreviated checklists. I found that both the DA-40 (!!!) and the Robin do not have "GPU-assisted start" checklists in the actual POH (let alone in the abbreviated checklists I use), and while the Piper Warrior has such a procedure in the POH, that procedure gets no mention into the two abbreviated checklists I have here (from two different operators).
The second factor is that if the crew (or single pilot, let's not rule that out) even knew that such a procedure existed in the POH, did he remember at the correct time? We don't know what kind of flight it is, whether he had (potentially nervous) passengers around and such. But we can assume that he was under a little more stress than usual. After all, if you find yourself preflighting an aircraft and discovering the battery is flat, you may have to do all sorts of things that you've never had to do before: find a GPU and somebody knowledgeable and willing to assist you with it (and will that person have specific experience with the DA-42, or only with more traditional twins & singles?). Find the GPU receptacle, possibly discovering that the standard plugs do not fit. The stress of having somebody walking very close to the fuselage with the engines running. And the stress of all your mates looking at you at the clubhouse, because this is something out of the ordinary and that attracts attention by default. Now you can argue that one of the things a pilot needs to do is manage stress, and that all this should not impact your performance, but you have to admit that this may just be a factor in not starting to read the POH, looking for the appropriate checklist.
And the third factor is that the POH may not be of much help anyway. I just read through the Warrior POH with regards to the external power startup (admittedly, first time I ever read that part, didn't even know it was in), and basically it comes down to this:
- All electrics off
- Connect GPU
- Normal start according to normal start checklist
- Lowest revs as possible
- Disconnect GPU
And that's exactly what I would have expected it to say. The GPU is connected, replaces the function of the main battery so you can do a normal start, and you've got to be careful while somebody removes the GPU. I even can understand that with a twin the procedure would be to connect the GPU on the left hand side, then start the right hand side, disconnect, start the left hand side. But I would read that as a safety issue with regards to the person disconnecting the GPU, not something that would assure a sufficiently charged battery to raise the gear (far later into the flight). So if I were to find out that after starting the first engine and disconnecting the GPU, the second engine wouldn't start? I would hook up the GPU again and start the second engine.
As I said before, yes, formally we've got to use the POH and SOP with everything we do. But in reality, things are not that simple, for starters because the POH itself is way too bulky to keep on your lap throughout the flight. So we use abbreviated checklists, improvise when necessary, do things from memory and even forget things from time to time. The aircraft should be designed so that this does not lead to a potentially deadly incident, which EFATO clearly is. So if it is possible to get into a situation where you have both engines running but a depleted main battery (either though an improperly executed GPU procedure or in the situation where the battery just had enough juice to start two engines but then gave up the ghost) then the aircraft should be designed so that at the very least, when you raise the gear, the engines keep on running.
The DA-40 has ECU backup batteries which cannot be depleted except in case they run the ECU. As far as I'm concerned, that's a good start. Without something like this, it's an accident which can happen again, despite the procedure in the POH.
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This will be my last post on the matter as I have said it is not really my scene.
In reply to 'confabulous' and to reassure 'B2N2' I agree that the pilot broke the rules in he did not adhere to SOP and the checklist - and for that he paid - fortunatly not with his life. It still begs the question as to whether the fact that this happened does not expose a deeper and far more alarming design failure by 'whoever', and a failure that needs an urgent fix.
You say neither Diamond or Theilert will back down. It matters not one jot whether they do or they don't. If they don't EASA will mandate and that is an end to the matter! They will mandate sooner rather than later which is just as well. It will also be a sad end to a 'marriage made in heaven'.
As for SOP and using the checklist, I was brought up in a tradition of ALWAYS using it and I am totally sympathetic to B2N2 on this issue. I have friends who remained in aviation and are now senior 747 captains or recently retired from such posts and own their own aircraft. In my experience they are almost all religious in their use of a checklist even on a basic Cessna. It is the new PPL's who seem to have a more cavalier attitude.
As for knowing the aircraft and the systems it is very worthwhile. As for fooling with CB's I don't think that's too clever. The SOP and checklist was designed by people who know the aircraft far better than a 'mere driver' will ever do. They are in all probability far better educated and probably far smarter and therefore it follows what they suggest should be treated with some respect. I have had too many young F/O straight from flying school and with a new type rating burning a hole in their pockets who suffered from what I called 'the flying hands' desease! Little hands seemed to have an affinity for pulling little round things in flight. They were just trying to impress but on occasions I have had to say "just sit on your hands and don't touch anything".
It seems I agree with Mike Cross. I wonder if it is the same Mike Cross who attended the same airline flying school as me all those years ago. If it is he will remember the ARB lectures in the wooden hut where we were taught about system redundancy! If it is we also flew in the same airline together. Check your licence number - it probably rather dates us both!
I am not about to cancel my order for a DA42 as I know one party in the dispute will be forced to back down and there will be a proper fix. I am also conscious that all new aircraft, particularly revolutionary ones like the DA42, will have a list of AD's. I ordered the aircraft with my eyes open. I am aware that the Malibu/Mirage had a terrible time here and the whole fleet was grounded for a while which rather frightened me off them.
The important lesson is to learn quickly from incidents and do something positive about it rather than argue the toss over it!
Happy days - I hope!
In reply to 'confabulous' and to reassure 'B2N2' I agree that the pilot broke the rules in he did not adhere to SOP and the checklist - and for that he paid - fortunatly not with his life. It still begs the question as to whether the fact that this happened does not expose a deeper and far more alarming design failure by 'whoever', and a failure that needs an urgent fix.
You say neither Diamond or Theilert will back down. It matters not one jot whether they do or they don't. If they don't EASA will mandate and that is an end to the matter! They will mandate sooner rather than later which is just as well. It will also be a sad end to a 'marriage made in heaven'.
As for SOP and using the checklist, I was brought up in a tradition of ALWAYS using it and I am totally sympathetic to B2N2 on this issue. I have friends who remained in aviation and are now senior 747 captains or recently retired from such posts and own their own aircraft. In my experience they are almost all religious in their use of a checklist even on a basic Cessna. It is the new PPL's who seem to have a more cavalier attitude.
As for knowing the aircraft and the systems it is very worthwhile. As for fooling with CB's I don't think that's too clever. The SOP and checklist was designed by people who know the aircraft far better than a 'mere driver' will ever do. They are in all probability far better educated and probably far smarter and therefore it follows what they suggest should be treated with some respect. I have had too many young F/O straight from flying school and with a new type rating burning a hole in their pockets who suffered from what I called 'the flying hands' desease! Little hands seemed to have an affinity for pulling little round things in flight. They were just trying to impress but on occasions I have had to say "just sit on your hands and don't touch anything".
It seems I agree with Mike Cross. I wonder if it is the same Mike Cross who attended the same airline flying school as me all those years ago. If it is he will remember the ARB lectures in the wooden hut where we were taught about system redundancy! If it is we also flew in the same airline together. Check your licence number - it probably rather dates us both!
I am not about to cancel my order for a DA42 as I know one party in the dispute will be forced to back down and there will be a proper fix. I am also conscious that all new aircraft, particularly revolutionary ones like the DA42, will have a list of AD's. I ordered the aircraft with my eyes open. I am aware that the Malibu/Mirage had a terrible time here and the whole fleet was grounded for a while which rather frightened me off them.
The important lesson is to learn quickly from incidents and do something positive about it rather than argue the toss over it!
Happy days - I hope!