flaps on always-hot bus?

[prkaye]

What do people think of putting the flaps on the battery (always-hot) bus? I'm thinking in terms of flaps being safety-critical.

[PCHunt]

IMHO, flaps are not at all flight critical. If they fail in the up position, you just make a no-flap landing, which you will have been practicing regularly.

And if they fail in the down position, the airplane has plenty of power to go around, even at full gross weight. You will have practiced this maneuver occasionally, as well.

[frankh]

I guess it depends..I mean the RV will land quite happily without flaps if you've got 3000ft of runway.

I think I put mine on the "normal" buss just because its less equipment that could drag down the battery volts in the event of a catastrophic failure.

No cast iron rule about it though.

Frank

[GregM]

I have aft mounted batteries and I ran a fused wire directly from the battery to the flap motor. I thought it would be wise to exclude it from all other busses. Hopefully, if all else fails and I still have some battery left, I could get the flaps down even if I had to shut down the busses for an electrical problem. Something to think about.

[erich weaver]

I think you are ok either way. Obviously flap operation is only brief, so you are not really adding to the load that the e-bus will be supporting. And if you leave it on the main buss and have turned that off to conserve amps during a electrical problem event, you can always re-activate the buss shortly before landing when you have the runway made. This would also let you use landing lights and other goodies on the main buss for the short time that you will really want them, while retaining the simplicity of simply switching to the e-buss to shed non-essential loads.

erich

[N941WR]

Phil,

This falls under the “what is absolutely necessary to get you on the ground safely” category.

I have easily landed my -9 on our narrow 2300' strip w/ trees at both ends without flaps with lots of room left over.

The answer is yes, you can put them on the always-hot buss but that means you should have a way to shut them off, should your switch fail in either the up or down position. A pullable breaker is what I used.

Remember, that anything on the always hot buss could cause you to drain the battery down when you are away or possibly cause a fire should it short out while in the hangar. Of course, this could happen even if you didn't have an always-hot buss.

Are you possibly confusing the always-hot buss with an e-buss? If so, do a search, there have been a lot of discussions on what should and should not be on the e-buss.

In my simple VFR craft, only the keep-alive circuits for the EFIS and EMS, a courtesy light attached to the bottom of my tip-up's roll bar, and "power port" w/ heavy wire and a 7.5 amp breaker are on my always-hot buss.

Everything else is either on the main buss or the avionics buss.

One minor tip: Don’t label the “Keep Alive” circuit “Keep Alive”, I had more than one passenger see that and question me about it.

[Jamie]

I land my nosedragger with no flaps in about 1000 feet. As already mentioned, flaps are non-critical. If they were critical, they wouldn't be electric in my plane. :-)

[Sam Buchanan]

Originally Posted by prkaye

What do people think of putting the flaps on the battery (always-hot) bus? I'm thinking in terms of flaps being safety-critical.

That is the way the flaps on my RV-6 are wired, straight to the battery via an in-line fuse at the battery.

The reason I wanted the flaps always hot was for convenience, not a "fail-safe" reason. I like being able to lower and raise the flaps without the master being on. This comes in handy in the hangar during cleaning, and makes it easier to raise the flaps prior to engine start before the master is switched on.

This is strictly a personal preference deal, do whichever you think will work best for you. As long as you fuse the flap power lead, I can't see any reasons for not having "hot" flaps. I guess a stuck switch might be an issue, but the flap motor will run with no harm when it hits the end of the travel, and what are the odds a flap switch will fail closed while the plane is sitting in the hangar?

[the_other_dougreeves]

As others have said, flaps are not critical to flight. If you do put them on the e-bus, make sure your fuses are appropriately sized.

TODR

[SteinAir]

Those of us that had to live through the old "fail every 40 hr." flap motors got used to flying with no flaps. RV flaps just aren't that critical and don't make a drastic difference. Not to be sarcastic, but if you can't get it down in less than a couple thousand feet without flaps....well....go practice because it's easily doable, even with a FP prop. As others have said, 1K-1500' should still be doable.

As Sam said it's a personal choice, but my opinion is only put stuff on the hot buss that is critical to continued flight. Flaps just aren't something that would be considered safety critical in an RV.

My 2 cents as usual.

Cheers,
Stein