Generator to Alternator Conversion

[aquanaut]

HELP!!! ... I have a '48 170 with a 13 amp generator installed on a O-300 B. My plan is to convert to a alternator. I got the 337's that others have done for this conversion from headquarters and went through them with my mechanic. We chose the one that best fit our intentions and submitted a new one to the FAA. Thinking we'd save some time I purchased the necessary components while waiting on the approval of the 337. Here's where the problem comes in. We finally heard back from the FAA and were told theres no way he could approve the 337. He said the Feds are really tightening up on approvals for that kind of conversion (I've heard of other instances). The inspector did say if I had a more recent copy of an approved 337 (within the past year) he could approve it.
If anyone has made this conversion in the past year I would be eternally greatful for a copy of your 337. Or if anyone has an idea for another plan of attack I'm all ears.
Any and all help will be appreciated.
Thanks Dave
'48 170 N2646V

[davevramp]

I am in the same situation that you are the FAA will not aloe a 337 so I went to a STC Below is the info for the Stc I am using. If I can help let me know.
Dave


BARNSTORMERS AVIATION
911 Sportsman Neck Road, Queenstown, MD. 21658
Tel: 410-827-7896, E-mail train@intercom.net

ALTERNATOR INSTALLATION INFO, ALL AIRCRAFT

Our installation utilizes a Ford/Cessna 60 amp alternator that bolts directly onto the C-85, C-90, O-200 and O-300 engines. The installation is a standard alternator circuit providing a nominal 14 volts for aircraft with 12 volt battery systems.

The following parts would be required:

Alternator
Voltage regulator
60 amp ammeter
Voltmeter (panel-mounted). Our STC lists a combination gauge that allows a constant ammeter/voltmeter readout. (Not required for Cessna 120/140/140A).
circuit breakers
noise filter
other minor parts for alternator drive and blast tube assembly

We provide the Supplemental Type Certificate, full instructions and schematics, and a list of suppliers for parts. We do not provide parts for Aircoupe or Cessna 170. However, we do stock the VR600A voltage regulator for the Cessna 120/140/140A. As of this date we are the only supplier for that part. A rough estimate of parts cost is $800 to $1000.

Aircoupe and Cessna 170 owners: to order, please send a check or money order for $85.00 and include aircraft type, registration number and serial number.

Cessna 120/140/140A owners: to order, please send a check or money order for $204.00. This cost covers STC, voltage regulator, and shipping. In addition, I will need your aircraft type, registration number and serial number.

I am certain that you will be pleased with the dependability and performance of this installation. It is one that has been used for many years, and continues to be quite popular in small aircraft. If you have any further questions, please call us.

Sincerely,
Fred Lagno

[zero.one.victor]

Dave, I have the 60 amp Ford/Cessna alternator in mine & it has worked flawlessly. Mine was FAA field-approved via 337 back in 1994, using Cessna parts. The STC referenced above is a real bargain at $85 as it allows simple IA signoff on the 337, instead of requiring (difficult-to-impossible) FAA field-approval. Or there are some other STC'd conversions available which (I believe) include all the parts needed. My Spruce catalog shows an STC'd Skytronics/Jasco 50-amp alternator kit for $916.
But if I was you, I'd consider a simple upgrade to a higher-capacity generator. Both the 25 amp & 35 amp generator are approved on the TCDS (items 305 & 306). The 35 amp generator can only be installed on an engine with a dampened crankshaft (must have a "D" in the engine serial number) but I believe the same restriction applies to the alternator also. You would still have to replace the regulator, circuit-breaker/fuse,some wiring, and probably the ammeter, but I bet it would be way cheaper than the alternator conversion. The March & April Flypapers both had ads from members trying to sell generators, probably people who did an alternator conversion, or you could buy a brand-spanking-new generator from Spruce (about $200 plus $200 core charge)or some other supply house. Either forfeit your core charge or maybe they'd even take your 13-amp generator (I think it's really a 12-amp,p/n 1101876) as a core.
The main drawback to a generator system is that they don't charge at low rpm. If you do a lot of night-time ground op's you might have trouble keeping the battery charged up.And the TCDS lists the 35 amp generator at 19 pounds, an alternator might be somewhat lighter. On the plus side, generator systems are simple to troubleshoot and fix, and would maybe save you some dough. You should talk this over with your mechanic.
Let us know what you do.

[N2865C]

I have done the BARNSTORMERS AVIATION alternator conversion on a C-85 and was very happy with the results. Fred was very helpful when I had questions.
jc

[GAHorn]

And another good point about a generator system is: IF you have a discharged battery and prop your airplane your generator will still come online and charge the battery, ...while an alternator will still be dead (without some external method of exciting it's field, it simply won't come online. Therefore your battery will remain discharged.)

An important consideration about the purpose of a battery: It is NOT for starting your engine....although that's what we most frequently use it for...that's just a convenience.
The REAL PURPOSE of a battery is: 1) to provide a stored source of emergency electricity for when generated electricity fails, in order to keep lights and avionics running until we can get on the ground, and 2) to provide a "shock-absorber" (after all, it's just a large capacitor/condenser) for our electrical system, and prevent surges/spikes from damaging equipment.

[aquanaut]

Dave, got your post, called Fred, he was very helpful. I'm mailing him a check today. Frotunatly its the same alternator I have on hand. Thanks for the post.

[N4281V]

Has anyone done the Barnstormers STC on a O-300-B engine? My understanding is that the STC does not cover it, but has anyone gotten a field approval for it? And if so, when did you do it...recently? or a while ago?

Thanks...