General Category => Helio Modifications => Topic started by: rmartell on March 30, 2014, 07:52:43 PM

Title: STC for 28volt alternator
Post by: rmartell on March 30, 2014, 07:52:43 PM
Does anyone have information on a 28 volt alternator STC for a 295?
Title: Re: STC for 28volt alternator
Post by: rmartell on March 30, 2014, 08:07:03 PM
Sorry Jim,

Just found the earlier post he had on the subject back in January.

Back then to the other question...Does anyone know if I can use a M-2, 28 volt - 50 amp generator from Accessories, Inc on my Helio?

If not, does anyone have a 24volt-100amp generator and regulator for a G0480?
Title: Re: STC for 28volt alternator
Post by: Doug Johnson on March 30, 2014, 10:52:34 PM
I believe the M-2 28 volt is what you need attached a photo of the line in the illustrated parts catalog.


If you decide or have to get the 24V 100 amp gen make sure it will fit first. The GO-480 that came with my Helio was a brand new O time Military surplus engine and had a 24V 100 amp gen and 24V starter I liked 24V (because you can use smaller wire less weight copper is heavy) and converted the rest of the airplane to 24V and intended to use the 100 amp generator because it came with the eng. Even though it was heavy the price was right. When we went to install the Gen it would not fit because it hit against the firewall.

You don't really need a 24V 100 amp gen it is the equivalent of, in watts, a 200 amp 12 volt generator and it is heavy. I went with the 24V volt Jasco alternator as discussed earlier.

Unless you anticipate some unusual power requirements. A 50 amp 24 volt (equivalent to 100 amp 12 volt) is plenty and if you were to go all LED lighting which uses a fraction of the watts used in incandescent lighting plus new avionics which use less power than earlier equipment that is far more than you need.

If I remember correctly the gen or alt is rated at 80% continuous load, and 100 amps at 12V is a lot, most single engine aircraft only have a 50 or 60 amp 12 volt gen or alt. The biggest emerg backup that I've seen put on the Vac pump pad is 30 amps at 12V, although that may be because of torque load on gears.

Title: Re: STC for 28volt alternator
Post by: airshiptv on March 31, 2014, 10:36:09 AM
We have some experience with this.  The U-10 had a cutout in the firewall for the added length of the military generator.  Frankly I would stay away from them.  Jasco is really the only option because of coupler issues.  Even the 12v 50 amp is fine for daytime and if you go with LED lighting it is fine for night.  Somewhere in AC 43.13 ? it states you can use 100 per cent if you have a direct readout of the alt load.  Remember most systems only measure the charging system.  You really do not know how much the alt or gen is putting out.  We did that and its great for trouble shooting.  We can measure both volts and amp directly from the alt.  In the early days of our operation we were using 55 amps at night covering games with the 12 volt plane with a 70 amp alt.  LED nav and strobe lighting dropped that down almost 10 amps.  New equipment has dropped it even more.  Of course the 28 volt plane drops the amps in half. 
Title: Re: STC for 28volt alternator
Post by: Doug Johnson on March 31, 2014, 12:48:29 PM
I agree with airship on the 100 amp gen mainly because what good is a firewaLL with a great big hole in it the little holes for controls wires and such are bad enough and the medium size holes for the heater and air ducts are worse.

My mechanics used a sledgehammer to try to put a dent in the firewall so it would fit it didn't work and made my brand new stainless firewall look like crap. I was not happy. If you really needed 100 amps You might remove the firewall and take it to a shop that had a ten ton hydraulic hammer and stamp in a dish that would allow you to put the 100 amp gen on. but you would have to partially pull the eng if you ever wanted to change it.

50 amps at 24V has the same watts as 100 amps at 12V.

By the way the 24V starter turns the eng over a lot faster easier and longer than the 12V starter even in cold weather.

Use two 12V batteries in series and you have lots of cold weather canking and a center tap between the two batteries gives you a 12 volt power source for your portable electronics.

Title: Re: STC for 28volt alternator
Post by: airshiptv on March 31, 2014, 07:29:57 PM
Actually the cutout on our firewall has a "dish" riveted into a cutout directly behind the alt   Maybe 2-3 inches at its deepest.
Title: Re: STC for 28volt alternator
Post by: lbpa18 on March 31, 2014, 08:03:25 PM
I feel compelled to pass on a "Lesson Learned" here. When checking out in our 295 having recently purchased it, I was doing some pattern only work. I had all the outside lites on, strobes, nav, both landing lites, one nav/comm, one comm on 121.5, transponder. Fuel boost pump on just prior to landing until shortly after takeoff, high RPM during takeoff, medium RPM on downwind, etc.  The Jasco fried. Troubleshooting an expensive R&R of Jasco, I re-verified the elec load. Basic math adding these loads did not account for two problems I had that many of us may also have. My batteries were tired so there was a large recharging load from after engine start, and the Jasco was old and likewise tired. Loading it up so much pushed past it's ability. Now, I account for the charging and am very careful how many of these electrical Loads I put on the Jasco until I am at high RPM where the Jasco is putting out to its capability. Not only will mismanagement of these loads be expensive, but it may leave me stranded far from help on some lake or river here in AK.
Title: Re: STC for 28volt alternator
Post by: airshiptv on April 01, 2014, 10:01:02 AM
A perfect example of why a second Volt/amp meter is so useful.  In this case I would think you would have found a high charging amp draw but again no idea of what the alt was doing.  When we lose an alternator in flight we try and get a ground APU hooked up to charge the battery while we replace the alternator.  If we don't we can see an almost 20 amp extra draw just for charging the discharged battery.