BC12-D A65 to A75 Conversion

[barnstmr]

Re: BC12-D A65 to A75 Conversion

Who is your DER in Georgia? Is it Bob Minnis? Tell him if he has any Taylorcraft compliance questions, to give me a call. He has my number.
Good Luck.

[CStence]

Re: BC12-D A65 to A75 Conversion

If it is stamped A65 that's what it is. The dash numbers are considered by Continental to be modification levels of the engine model. I believe the front of the parts manual describes this.
There is a Service Bulletin that covers the changing of the dash numbers with-in an engine family. You might be worrying about a situation that doesn't exist.
EO

I don't think this is the case. The only engines that can be installed for the BC12-D are listed in the Type Certificate as: A65-8 (Taper Crankshaft), A65-8F (Flange Crankshaft) and A65-8J (Fuel Injection). Just as I can't install an A65-9 (different accessory case for starter) as a minor alteration since it is stamped "A65" on the data plate, I can't install other dash numbers because the engine family is A65.

You are right that Continental SB M47-16 talks about changing within the engine family. If it was simply a matter of changing from one engine dash number to the other, this can be done as a minor alteration since approved data exists for the change (ie SB M47-16). I've done this for C75 to C85 conversions. The issue at hand though is that no approved data exists for installing the -14 engine on the T-Craft.

[Edwin Otha]

Re: BC12-D A65 to A75 Conversion

If it is stamped A65 that's what it is. The dash numbers are considered by Continental to be modification levels of the engine model. I believe the front of the parts manual describes this.
There is a Service Bulletin that covers the changing of the dash numbers with-in an engine family. You might be worrying about a situation that doesn't exist.
EO

[CStence]

Re: BC12-D A65 to A75 Conversion

Lots of people will install the A75 components as a reliability upgrade. The only way to get the power is to spin it at 2600 RPM. If your prop limits the engine at 2300 it only makes 65 HP.
If the plate says it's a 65, it's a 65, regardless of your letter.
EO

Oh yeah,...the plate is clearly stamped "A65-14" with the take-off HP listed at "75HP at 2675RPM." So really, it is even more surprising that it has gone all these years without catching the eye of an IA. Oddly enough, they have been operating it at A65 RPM ranges (per the prop pitch) so they weren't even getting the benefit of the higher HP.

[CStence]

Re: BC12-D A65 to A75 Conversion

I'm not really following you on the problem. What ever this -14 engine is it still has a max continuous rating of 65 horsepower. The only increase is in take off power. It's still an A65 and shouldn't need any paperwork to justify the installation. Unless there is more to this story.
EO

The -14 engine actually makes 75HP at 2675RPM, which means whenever this engine is installed it probably has a higher operating RPM, just like an A75 does.
However, even if this was the same 65HP, it is still considered a major alteration because what is installed is different than what was originally installed (-14 as opposed to -8). That increase in HP (15%) makes it not only a major alteration, but one that can only be approved with an STC, according to the FAA. What I want to do now is de-rate the engine and operate it at 65HP (Not exceeding 2350 RPM in level flight). This should be straight forward since the engines are nearly one and the same (if operated the same).

Update: I have contacted a DER in Georgia who has been very helpful should approve the data for this (derated -14 installation) just as soon as I type it up for him. Then I'll just have to send the 337 to Oklahoma and we're home free.

[Ragwing nut]

Re: BC12-D A65 to A75 Conversion

Update:

I've heard back from the ASI at the FSDO. I asked him if I could get an approval to simply de-rate the A65-14 to 65HP at 2350RPM (via the prop). In this way the aircraft could be airworthy until such point that I get a one-time STC for the extra hp.

He claims that FAA Order 8900.1 precludes him from doing that because it was previously installed. I told him that I have grounded the airplane and am awaiting the approval before it goes any further...even going so far as to say that I could literally remove the engine and reinstall it so it would be a fresh install. The ASI replied that while there is no rule against that in the FARs I would be "convaluting" the rules. He went on to say I shouldn't "stick my neck out" for a pilot, almost as if I would be stirring up trouble for myself if I pursued this further.

I've got a call into the manager to question him on this but I'll be honest - the thought of making enemies at my FSDO is not a pleasant one.

I am sure he probably does not know the difference between a j-3 or a dc-3. Try and contact eric minnis, member here, he use to be FSDO in that area, but not sure if he is still FSDO. If need be, I would pull cylinders and convert back to -8 via continental sb and be done with it.

[Edwin Otha]

Re: BC12-D A65 to A75 Conversion

Lots of people will install the A75 components as a reliability upgrade. The only way to get the power is to spin it at 2600 RPM. If your prop limits the engine at 2300 it only makes 65 HP.
If the plate says it's a 65, it's a 65, regardless of your letter.
EO

[Popsdory]

Re: BC12-D A65 to A75 Conversion

Is there any way that I can just look at my engine to see if it is a 65 or 75? I mean other than the data plate? It sounds like all of the parts to change it are internal is that correct? My logs data plate etc. say 65 but there is a letter from one owner to another included in the logs that says it was upgraded to 75 at overhaul.. As far as anyone is concerned, it's a 65, if I toss the letter right? Or can it be seen? Still has the stock 65 prop.

[Edwin Otha]

Re: BC12-D A65 to A75 Conversion

I'm not really following you on the problem. What ever this -14 engine is it still has a max continuous rating of 65 horsepower. The only increase is in take off power. It's still an A65 and shouldn't need any paperwork to justify the installation. Unless there is more to this story.
EO

[CStence]

Re: BC12-D A65 to A75 Conversion

Update:

I've heard back from the ASI at the FSDO. I asked him if I could get an approval to simply de-rate the A65-14 to 65HP at 2350RPM (via the prop). In this way the aircraft could be airworthy until such point that I get a one-time STC for the extra hp.

He claims that FAA Order 8900.1 precludes him from doing that because it was previously installed. I told him that I have grounded the airplane and am awaiting the approval before it goes any further...even going so far as to say that I could literally remove the engine and reinstall it so it would be a fresh install. The ASI replied that while there is no rule against that in the FARs I would be "convaluting" the rules. He went on to say I shouldn't "stick my neck out" for a pilot, almost as if I would be stirring up trouble for myself if I pursued this further.

I've got a call into the manager to question him on this but I'll be honest - the thought of making enemies at my FSDO is not a pleasant one.

[CStence]

Re: BC12-D A65 to A75 Conversion

Barnstormer...
You are right. My FSDO kicked the 337 back rather rudely, stating that they weren't allowed to approve such a thing and I'll have to get an STC. THAT is going to be a headache. If I'm lucky the ACO won't give me much trouble for a one-time STC but more than likely they're going to want DER's and such. Sheesh. All for a measly 10HP. How is it the FAA got so smart in 2004 that now they know more than all of their predecessors?

The thing is, the owner is up the proverbial creek because he had his prop repitched and cut to 72"...it is now 1/2" too short for what the Type Cert allows. Even if I talk him into going back to the A65 he'll have to buy a new prop.


Ragwing...
The only information I've found on the A65-14 is what I qouted from the Type Certificate. The odd thing is that it appears the A65-14 makes 75HP at 2675 RPM whereas the A75 makes 75HP at 2600 RPM. That makes little sense to me, but that is what the Type Certs say.

[Ragwing nut]

Re: BC12-D A65 to A75 Conversion

I think Mike is looking for information from the factory. The pistons are waffled for more surface area when the oil hits them, no compression increase.
EO

The 75 pistons are waffled. and the 80 pistons are waffled, higher dome and 5 ring. there is a 3 ring and 4 ring 65 piston, but the tcds does not specify the actual parts.

I just read the data sheet and sounds like all the changes to make one a 75. I guess I will have to dig out one of my very old parts books and look.

[N96337]

Re: BC12-D A65 to A75 Conversion

You could call Lycon and get ahold of Loren Lemen... 559-651-1070 or email [email protected] ....he was a tech rep for Continental for many years, and just went to Lycon....I'd bet he could fill you in right off the top of his head. Great guy!!
John

[Edwin Otha]

Re: BC12-D A65 to A75 Conversion

I think Mike is looking for information from the factory. The pistons are waffled for more surface area when the oil hits them, no compression increase.
EO

[Pearson]

Re: BC12-D A65 to A75 Conversion

Mike,

I thought the TCDS pretty much listed out the changes needed to make an A65 into a -14. I suspect the pistons it refers to increase the compression.