Hypothetical - Robinson Total Electrical Failure

[RandomPerson8008]

Student pilot question:

If one were to experience an electrical failure(battery and alternator) in an R44, would you would lose (among other thing such as lights & radios):
(I understand that one should be forewarned of this by the alternator warning light, and that you would have at least 10-15 minutes before depleting the battery assuming some non-essential items were turned off)

1) Governor
2) Tachometers
3) Low RPM warning system

Studying the electrical diagram in the pilot's operating handbook, it appears that there is power for the Tachs and Low RPM warning system through the magnetos & clutch switch? Will these two systems remain powered with the loss of battery and alternator? I did not think the magnetos were capable of powering anything other than the spark plugs.



It appears that the rotor brake and rotor brake light continue with magneto/ignition system power as well?

How about the clutch actuator? Diagram seems to show magneto power to it too. I can't imagine there would be sufficient power to move the clutch actuator without the battery or alternator.

Thanks in advance. Please go easy, I am a mere student pilot and my instructors rarely have time to answer my questions outside the helicopter.

[TeeS]

Hi Random
Think about the systems that you might, or might not, want to be active when you engage the starter. Therein may lay your answer.
Cheers
TeeS

[RandomPerson8008]

During start I don't really want anything except power to the starter and tachometers, and as many engine indications/warning system as I can get without impeding current available for the starter, I guess. Raven I so there is no electric fuel pump. I know that rotor brake engagement defeats the starter, RPM under 80% defeats the governor, and collective full down (as it is during start) defeats low rpm warning.

I also realize that the tachometers receive power with both the battery and alternator switches off + clutch switch engaged, but the manual implies that the battery is still the source of their power in this configuration (via a wire bypassing the battery relay).

Mostly I ask because it seems crazy that if you lost the battery and alternator you would be flying without low rpm warning, tachometers, and governor. It would seem very difficult to fly the machine without all 3 of those. I was hoping they designed an alternative power source for some of those system but couldn't find a straight answer in the manual.

[Ascend Charlie]

Sit in the machine with no power. What is working? The clock. Via the battery relay bypass circuit. Pressure instruments. MAP. Skid ball. Balance string.

With battery still OFF, engage the clutch switch. Power now appears to go through it via the bypass circuit, to the tachos and a pile of other stuff on the 28v bus bar.

Start the engine, then turn the alternator and battery switches off. See what is still running. That bypass circuit is still alive, until the battery is depleted.

Then you don't have a lot. Your ears will tell you if the RRPM is right. Your eyes tell if the attitude is correct. Your left hand tells you how much power you are pulling. You have been trained in governor-off operations, so your ears will tell your left wrist how much to tweak the throttle. Eyes show if you are in balance, and how far above the ground you are. Fly yourself, using known power settings and attitudes, to a hover, and put it down somewhere that an engineer can get to you with some electrical assistance. Just don't do this at night.

[frisbee90]

Originally Posted by RandomPerson8008

I did not thing the magnetos were capable of power anything other than the spark plugs.

This is correct. I think you may be misunderstanding the purpose of the wires going from the starter switch to the magnetos. They are in actual fact grounding wires. When that wire leading to the mag is pulled to ground (at the switch), then the mag shuts off. This is useful so that a) you can check each mag is functioning individually and b) that if the engine is turned over with the switch in the OFF position (ie. both mags are grounded) the engine won't fire (more of carry-over from when the O-540 lives in a plane).

As such, in the event of both the alternator and battery going out you are very much out of luck regarding any and all electrical systems, and AC's post above regarding what instruments you do still have and how to use them to get on the ground is pretty well spot on.

An extra bit of mag wiring trivia - position R in the starter switch actually connects via a wire to the L mag to shut if off, therefore testing the R mag as it'll still be running, and vice-versa. The general electrical diagram in the RFM is really only a basic guide to the 'interconnectedness' of the systems, and for a true understanding of how it works and where the electrons actually go, you need the wiring diagrams in the Maintenance Manual - but they're not as easy to read!

And one final aside, if your instructors barely have time to answer good technical questions like these, then I'd be considering looking for another school, but that's just my 2c.

[RandomPerson8008]

Ok thank you all for the responses. I believe most light airplanes have independent power sources for tachometers, if not mechanical linkage, thus the question. Yes it would've been helpful if the electrical diagram were color coded +/- but I was just secretly hoping that the tachometers were more redundant than they are.

[212man]

I find it bizarre that the POH doesn't address this. Having just found it online, the only thing it says is that continued flight without a functioning alternator can lead to loss of tachometers resulting in a hazardous flight condition!

And one final aside, if your instructors barely have time to answer good technical questions like these, then I'd be considering looking for another school, but that's just my 2c.

I agree!

[RandomPerson8008]

Originally Posted by 212man

I find it bizarre that the POH doesn't address this. Having just found it online, the only thing it says is that continued flight without a functioning alternator can lead to loss of tachometers resulting in a hazardous flight condition!

I agree!

The confusing part about that statement in the POH is that the emergency procedure for losing the tach includes "use governor", which in electrical failure you will not have either.

I get it, though. Helicopters are weight critical and expensive enough without extra parts like small generators for the tach.

[SASless]

Your ears will tell you if the RRPM is right.

In as many words as you wish to use....define "RIGHT" as used in that statement will. you?

If either the Engine Tach OR the Rotor Tach fails.....that is one thing.

If both fail....that is an altogether different situation

If the aircraft is properly rigged....in autorotation with the Collective fully down....the Rotor system should maintain sufficient RPM to achieve a safe descent.

An overspeed of Rotor RPM in autorotation would be a far less serious event as compared to too low an RPM in autorotation.

So how does one Ear....accurately determine the Rotor RPM without the assistance of a Rotor RPM Indicator?

[aa777888]

Originally Posted by RandomPerson8008

Student pilot question:

If one were to experience an electrical failure(battery and alternator) in an R44, would you would lose (among other thing such as lights & radios):
(I understand that one should be forewarned of this by the alternator warning light, and that you would have at least 10-15 minutes before depleting the battery assuming some non-essential items were turned off)

1) Governor
2) Tachometers
3) Low RPM warning system

If you lose both battery AND alternator you will lose EVERY electrical system and device in the R44 (any variant) EXCEPT the magnetos. No governor. No tach's. No low RPM warning system. All gone except the mag's.

Studying the electrical diagram in the pilot's operating handbook, it appears that there is power for the Tachs and Low RPM warning system through the magnetos & clutch switch?

That is incorrect.

The electrical schematic that Robinson provides is almost worthless because it does not provide any detail of the circuitry or switching in a number of important components, most notably all relays. IMHO, as both a pilot and an electrical engineer, this is unforgivably stupid. You therefore have to infer how it all works from the rest of the POH, which you can do, but it's a PITA.

That said, the clutch, engine tach and rotor tach have two sources of power, which are combined on what is effectively an "essential systems bus", although it is not implemented as an actual bus. The electrons don't care, though! This is done in the clutch switch for the clutch, and by means of a diode isolator for the tach's. The two sources are the main bus via the master radio relay (in the version of the diagram--it sure as hell isn't an electrical schematic--which you posted) and a direct connection to the battery via contacts on the clutch switch which are closed when the clutch is activated (regardless of how poorly drawn the diagram is at the battery relay).

The design intent is that if you have an electrical fire in flight and perform the emergency procedure, which includes turning off both the battery and alternator switches, then you will still have the clutch and tach's remaining even when you do that because the battery will almost certainly last for the very few moments it takes to "land immediately". You will lose the governor and low rotor RPM warning system and that is explicitly noted in the POH emergency procedure. Obviously when certifying the helicopter it was judged a worthy trade-off to keep the clutch and tach's operating under these conditions. Certainly it is for the clutch.

Will these two systems remain powered with the loss of battery and alternator? I did not think the magnetos were capable of powering anything other than the spark plugs.

Again, those systems, and all other systems, will be gone if both battery and alternator are kaput. The mag's only run the ignition system, as you correctly surmise.

It appears that the rotor brake and rotor brake light continue with magneto/ignition system power as well?

No, those are fed power from the main bus via a circuit breaker, as is that connection to the clutch switch. Again, the Robinson diagrams are junk because they do not label inputs and outputs.

How about the clutch actuator? Diagram seems to show magneto power to it too. I can't imagine there would be sufficient power to move the clutch actuator without the battery or alternator.

Negative. See above.

Thanks in advance. Please go easy, I am a mere student pilot and my instructors rarely have time to answer my questions outside the helicopter.

You need to find some new instructors ASAP. Knowledge of aircraft systems is important, and they should be teaching you this. If they are not teaching you this, what else are they not teaching you? You don't know what you don't know!

[Ovc000]

Originally Posted by RandomPerson8008

Student pilot question:
Thanks in advance. Please go easy, I am a mere student pilot and my instructors rarely have time to answer my questions outside the helicopter.

Shocking!
Don't waste time, go to another training provider or demand another instructor.
The briefings/debriefings and answering questions are equally or even more important than the flying lesson.
Each 1 hour flying lesson should at least involve 1 hour of briefing/debriefing and answering questions.

[helicopter-redeye]

Who are you training with Random? Alt failure in an R44 is an emergency you could face (battery failure without the red Alt light fIrst is less likely) so you need to know how to address it before being qualified.

You can continue in flight without the Alt but you have limited time before loss of key instruments, transponder, radios, etc

Not a big deal but note, the AFM says Land as soon as Practicable, so you have time to divert and not panic.

Please talk to your instructor and get them to explain what to do for this key emergency.

H-R 01

[Hot and Hi]

Originally Posted by RandomPerson8008

The confusing part about that statement in the POH is that the emergency procedure for losing the tach includes "use governor", which in electrical failure you will not have either.

It sounds circular but it isn't.

- If both tach's fail, you can still perfectly rely in the governor to control engine RPM.

- If in a fire you decide to switch master OFF, you don't have a governor, but you can control RPM manually. Use tachs (that still work despite master OFF) to set for the right RPM

If after an ALT failure you run down your battery, you have NIL power, so neither governor nor tachs will work. If you are really good, you can still safely fly, or autorotate her to the ground. All others better land before the battery is finished.

How long will the battery last once the ALT failure light comes on? It depends. I'd say between 15 min and 60 min. It says, switch off non-essential equipment to preserve battery charge. RHC doesn't list what is non-essential, but don't forget to switch off the air conditioner, as its (electric) fans draw a lot of current.

Anybody have a recipe how to judge when the battery is about to die, before it dies? With only the Amp meter, and without a Volt meter, that's really difficult to tell. An idea would be to mentally note the Amp meter negative deflection when switching on, say, landing lights, just for a second. Then test this every 5 min or so. Theoretically, with an almost empty battery, the Amps the battery can provide to the landing lights will go to zero (i.e., lesser negative deflection of the Amp meter).

I don't know how reliably this works in practice. I have tried it once with an ALT failure, but managed to land before the battery died; all the time the battery provided sufficient Amps to the landing lights when I flicked the switch for test purposes. But I haven't seen for myself how the system behaves closer to the end...

[[email protected]]

Is it a NiCad battery? If so, you do know that they tend to 'cliff-edge'? ie good volts, good volts, good volts - no volts!

[Robbiee]

Originally Posted by RandomPerson8008

The confusing part about that statement in the POH is that the emergency procedure for losing the tach includes "use governor", which in electrical failure you will not have either.

I get it, though. Helicopters are weight critical and expensive enough without extra parts like small generators for the tach.

Why is this confusing to you? Tach failure and Electrical failure are two seperate emergemcies. Sure Electrical failure includes Tach failure, but Tach failure does not include Electrical failure. There's Governor failure too you know, as a completely seperate issue.

[Ascend Charlie]

So how does one Ear....accurately determine the Rotor RPM without the assistance of a Rotor RPM Indicator?

You don't need accurate, but your ear will tell you if it's way too high or getting way too low, just keep it on the high side.

Even old blokes like Sassy and me could pick up the difference, you young pups should have it easy.

[212man]

I get it, though. Helicopters are weight critical and expensive enough without extra parts like small generators for the tach.

Pretty sure it was facetious.

On the aural calibration topic - I was taught to fly constant speed prop FW with the RPM gauge covered up, and you soon learn to set the RPM accurately from the noise signature. (Assisted by a crusty old-school RAF QFI thumping your helmet!)

[RandomPerson8008]

Originally Posted by Robbiee

Why is this confusing to you? Tach failure and Electrical failure are two seperate emergemcies. Sure Electrical failure includes Tach failure, but Tach failure does not include Electrical failure. There's Governor failure too you know, as a completely seperate issue.

It's not so much confusing as surprising that there would not be an independent source of power for the tach (as it is in many light airplanes, to me the tach in a robinson would be a lot more critical), . I fully understand that they can fail independently.

Is it a NiCad battery? If so, you do know that they tend to 'cliff-edge'? ie good volts, good volts, good volts - no volts!

POH says it's lead acid.

Thanks for all the replies. My questions have been answered so I will bow out. I don't have any choice in flight schools, so it is either this or I quit. Also helicopter flying for me is just for fun, I have no ability to do it professionally because of fixed wing flying obligations.

[TeeS]

HI again Random
Sorry for the very quick, off the cuff, response earlier. I only had a chance for a very quick look at the diagrams etc. before I set off travelling. From that it looked like the connection you were discussing might involve inhibition of starting if the rotor brake is applied or clutch is engaged rather than any kind of power supply. I'm afraid I still haven't had time for any kind of deeper look and it is nearly thirty years since I last flew a Robinson. Generally these diagrams are rather simplified for us simple pilots :-)
Cheers
TeeS

[Twist & Shout]

The throttle corelator is good.
If the alt failed and flight was continued until the battery was exhausted the RPM would remain in a safe range (with no throttle change) though out almost all gentle flight regimes.

So while not recommended. One could stay in the cruise for a long time, make a gentle approach and landing. Without changing the throttle.
Using “the ears” for gross error is always recommended.