Correct mechanization for powering vertical gyros/autopilot channels in the event of generator failure?

[primus_TR]

Hello folks, 

The other day I got shot pretty badly and both my generators were inoperable. So, I decided to follow the emergency procedure described in the Cold War Museum Hind 24 manual to power the AC and DC buses from the APU generator:

1. Started APU.

2. Started APU generator.

3. Switched ON Power from Battery switch

4. Switched ON PO-750 (115V) inverter

5. Switched ON AC External Ground Power switch 

6. 115 VAC BUS reads 115V

7. DC Rectifier BUS 1 and 2 both read around 30 Volts

8. DC Rectifier 1 reads 30 Volts, Rectifier 2 reads 0 Volts

I cannot read the voltage on the 36VAC buses so, not sure if they are powered.

In this setting, the vertical gyros do not work, and neither do the autopilot channels, although I have both the DC buses, and the 115 VAC bus powered. 

I tried this same procedure at cold start, and with the ground power connected, gyros work. But not when powered from the APU generator + 115V inverter. 

I have also noticed that when ground power is connected, generator channels (A-B) (A-C) (B-C) all show around 200 volts, although the generators are off. 

My end goal is to be able to operate the autopilot channels in the event of both generator failure during flight.

Most likely I'm missing a step, a switch or something in the procedure.

Any suggestions would be appreciated. 

 

Edited May 10, 2024 by primus_TR

[admiki]

I never tried it, but why would you turn on ground power?

From layman's perspective, that might be your issue, since that switch isolates circuits from one another

[primus_TR]

42 minutes ago, admiki said:

I never tried it, but why would you turn on ground power?

From layman's perspective, that might be your issue, since that switch isolates circuits from one another

That's from the procedure described in the CW museum manual. When it's off, the 115VAC bus is not powered, showing 0 volts.

[JetCat]

You mean the Hind is THAT AWESOME realistic that in events of failures real procedures described by maintenance engineers or museum manuals can be used - and it works?

DCS is clearly the best and most realistic flight simulator I ever had!

[AeriaGloria]

15 hours ago, primus_TR said:

Hello folks, 

The other day I got shot pretty badly and both my generators were inoperable. So, I decided to follow the emergency procedure described in the Cold War Museum Hind 24 manual to power the AC and DC buses from the APU generator:

1. Started APU.

2. Started APU generator.

3. Switched ON Power from Battery switch

4. Switched ON PO-750 (115V) inverter

5. Switched ON AC External Ground Power switch 

6. 115 VAC BUS reads 115V

7. DC Rectifier BUS 1 and 2 both read around 30 Volts

8. DC Rectifier 1 reads 30 Volts, Rectifier 2 reads 0 Volts

I cannot read the voltage on the 36VAC buses so, not sure if they are powered.

In this setting, the vertical gyros do not work, and neither do the autopilot channels, although I have both the DC buses, and the 115 VAC bus powered. 

I tried this same procedure at cold start, and with the ground power connected, gyros work. But not when powered from the APU generator + 115V inverter. 

I have also noticed that when ground power is connected, generator channels (A-B) (A-C) (B-C) all show around 200 volts, although the generators are off. 

My end goal is to be able to operate the autopilot channels in the event of both generator failure during flight.

Most likely I'm missing a step, a switch or something in the procedure.

Any suggestions would be appreciated. 

 

 

While it is emergency procedure for lost generators, it is only for 30-60 minute RTB using battery and APU, since each last only 30 minutes 

If you look in the Cold War museum manual at what is powered by the generators, and what can be powered by battery/APU gen with everything turned on, you will see that batttery/APU gen cannot cover every thing that the huge generators can. 
 

For example gyroscopes, they need the high voltage of the 240 VAC 400 hz generators. Nothing else can do this. So you cannot turn them off if you have generator failure. You just have to fly without them 

This line from it “The DC system and AC inverters can be operated on the ground with the main engines shut down using the APU starter / generator.” the inverter turns AC to DC, so there is still no proper full powered AC source with just battery and APU gen 

It also says that in emergency mode, which usually kicks in automatically, only IFF/radar alt/RWR/jammer/vibration/fuel gauge/red lights/PTIT are powered 

However, AP depends on gyros. Just reading it, it says that 36 VAC 3-phase transformers give the gyro 1 power. And that in emergency mode (PT-125 inverter on) gyro 2 is given power. So maybe try switching the gyro selection from vertical gyro 1 to vertical gyro 2 

However, AP still needs 36 VAC at 400 hz to operate. So the 115 VAC transformer is imperative here

Official instructions for double generator failure are  
“-set switches of both generators, rectifiers and transformers to the OFF position;
-open the caps and set switches PT-750A and PT-125U of the inverters to the ON position;
-Select selector switches TRANSFORMER -115V, TRANSFORMER 36V, PRESS GAUGE XFMR to the STBY position;

-Switch oťf all electric power consumers which are not required under given circumstances; in all cases' the controi instruments ťor power plant, fuel gage, vertical gyro No. 1 with roll and pitch indicator shall remain switched on, as well as the heating of LFI pitot tube at an outside air temperature oť 5.' C and lower.” 
start the AI.9B engine (it is allowed up to an altitude of 4,000 m), set switches APU GEN and POWER FROM BATT to the ON position and check voltage in the helicopter onboard power system as per voltmeter. Discontinue tlre mission and perťorm landing on own airfield, the nearest airfield or a selected landing pad proceeding from the 30-min maximum time of continuous operation of AI-9B APU;………
Power reserve oť the batteries is enough to energize the consumers connected to battery bus for about 9 min of flight (for I min - with search-and-landing light and taxiing light turned on).

[primus_TR]

8 hours ago, AeriaGloria said:

Official instructions for double generator failure are  
“-set switches of both generators, rectifiers and transformers to the OFF position;
-open the caps and set switches PT-750A and PT-125U of the inverters to the ON position;
-Select selector switches TRANSFORMER -115V, TRANSFORMER 36V, PRESS GAUGE XFMR to the STBY position;

-Switch oťf all electric power consumers which are not required under given circumstances; in all cases' the controi instruments ťor power plant, fuel gage, vertical gyro No. 1 with roll and pitch indicator shall remain switched on, as well as the heating of LFI pitot tube at an outside air temperature oť 5.' C and lower.” 
start the AI.9B engine (it is allowed up to an altitude of 4,000 m), set switches APU GEN and POWER FROM BATT to the ON position and check voltage in the helicopter onboard power system as per voltmeter. Discontinue tlre mission and perťorm landing on own airfield, the nearest airfield or a selected landing pad proceeding from the 30-min maximum time of continuous operation of AI-9B APU;………
Power reserve oť the batteries is enough to energize the consumers connected to battery bus for about 9 min of flight (for I min - with search-and-landing light and taxiing light turned on).

Very helpful, thank you