Crow Advice - RC Groups
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Sep 15, 2017, 11:09 PM
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Discussion

Crow Advice


Nearing the end of a build of a home brew "full house" ship and need some advice.
I've been reading some threads on crow and recommended setup files for the DX8 and my head is starting to hurt.

Just so we're on the same page I'm understanding crow to be full (untrimable) down flaps with ailerons up acting as outboard spoilerons operated by the throttle stick.

That said I'll outline my wish list and ask if you guys think it's a reasonable or recommended starting point for someone with no full house experience who's chasing nice slow controlled landings.

Using 2 of the 3 available flight modes - I'll call them launch/flight and Landing
Launch/flight mode: full length flaperons with camber adjustment controlled by throttle stick (elevator compensated)
Landing mode: Fixed 2 position flaps on switch with compensation
Outboard spoilerons, reflex controlled by throttle stick (elevator compensated)
Trying to keep it simple

I'm not looking for a "gimme" setup, I willing to give the programming a go myself but I really want to know if I'm barking up the right tree.

Suggestions welcome ... and excuse me if I'm using the wrong terminology or lost the plot completely.

Pics of the ship that I'm having problems landing gracefully and the current build.
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Sep 17, 2017, 04:54 AM
F3B
satinet's Avatar
Crow should be down flaps, up ailerons, down elevator all controlled proportionally from the throttle stick in harmony.

Fixed down flaps is a very bad idea.
Sep 17, 2017, 09:17 PM
around Colombia
ShredAir's Avatar
Thanks, Tom, for putting it concisely. I read this yesterday, but couldn't find the words and didn't take the time.
In other words, crashbuilder, "what he said..."
Sep 18, 2017, 01:03 PM
Registered User
timmig's Avatar
While crow can be used---I've flown full house TD F3B and F3F ships for years--and NEVER liked crow!! Flaps are much easier to use and just as affective as crow for landings. Crow kills your lift and will reduce altitude quickly, but I never found and instance where I needed it--and using simple flaps was much more controllable for decent and spot landings. FWIW
Sep 18, 2017, 08:55 PM
Registered User
^+1

Completely agree with timmig.

Flaps on the left stick with elevator compensation.

If your radio supports it - have the left stick become a 'stick switch'. So that when you pull back 10% or so, it will switch into 'landing mode'. Have generous aileron rate, and generous aileron to rudder coupling for slow speed authority.

Leaving ailerons in section gives improved stability.

Make sure flaps are not coupled with ailerons in landing mode.
Sep 18, 2017, 09:14 PM
Registered User
Thanks for the input guys.

I was looking for a simple introduction to 4 servo wings and just realized that I never considered a standard flaps/aileron approach. All my past experiences have been with full length flaperon landings and they were disastrous! It didn't occur to me that flap/aileron landings would be a workable alternative now that I've got a 4 servo wing to work with .... had my mind set on crow as some holly grail of sloping. Wow just straight flaps ... go figure

Thanks, that's where I'll start. Any real advantage to having the full trailing edge ailerons in my projected Launch/ flying mode. Or should I just go with the KISS principle? I.e. Outboard ailerons and flaps.

Talk about a duh moment ...

Crash
Sep 18, 2017, 09:33 PM
Registered User
Highly recommend full TE control otherwise

Each flight mode the te can be adjusted (camber, in section, reflex).

Use flap to aileron coupling for roll.

Use elevator to camber/reflex (snapflap) for pitch.

Enjoy the learning curve. It is a fun part of the hobby. Fortunately lots of great folks here willing pour out their knowledge.

(Always more than one way to skin a cat though ... )
Sep 18, 2017, 09:35 PM
Brett
bjaffee's Avatar
Quote:
Originally Posted by crashbuilder
All my past experiences have been with full length flaperon landings and they were disastrous!
FWIW, dropping full span ailerons as landing flaperons tends to be bad news...it kills your roll authority, and makes low speed control very dicey. Most people opt for spoilerons in that case. Not quite as easy to use as flaps, but you retain roll authority.
Sep 18, 2017, 09:52 PM
Registered User
Thanks again, now that I've put crow on the back burner ..... "I can see clearly now the rain ..."

We've been dealing with the outer bands of Hurricane Marina big swells and some high winds ... the power just came back on.
Sep 18, 2017, 10:52 PM
More Pile-it than Pilot
mdennis's Avatar
First, get your ass into cover of some sort. You can't fly if you aren't around.

Crow is a worthwhile thing to have programmed. It helps control the energy your plane has as it lands. It's not really about slowing down and speeding up.

World class pilots are using it, guys that have to land on a 2" patch at an exact time, but they generally don't use much more than about 30%. Of course they can drop theirs to 90 degrees if they need to and have planes built to take a nose dive onto that 2" patch.

Guys flying slope don't really need it, but it comes in handy when you get back to the edge and don't really want to go around again or have a small landing area.

As the flaps go down, most people, and all the hot shot pilots that I have seen, have the ailerons go up just a little. I have seen the argument that as the plane slows down, the wing is losing lift and having the ailerons go up reduces the lift over that part of the wing and you need as much lift as you can when you are going slow. Hot shot pilots aren't landing that slow, they are more about getting down.
Dec 01, 2017, 11:37 PM
Registered User
Well it took forever .... but she is ready to go but I'm still having some issues with the "correct" 4 servo wing program.

My biggest concern is that I'm not sure what the recommended set up should be. Your comments have cleared up some of my misunderstandings..... but I'm still no sure about my flaps.

I have flaps and camber on the throttle stick
3 flights modes - 1. launch, 2. cruise and 3. land (cruise and land are identical for now)

Modes 1 & 3 - full span ailerons at high stick position (0) - ailerons and flaps uncouple as the stick goes down giving me variable flaps and independent outboard ailerons. Is this correct? or should my flaps still have some up (only) movement coupled with the ailerons as they descend?

Mode 2 - I wanted full span ailerons with a few degrees reflex / camber controlled by the throttle stick. Unfortunately I only get full span ailerons when the wing is reflexed, once the stick goes past position 1/3 to induce camber I only get outboard ailerons.

I could solve this by having separate reflex and camber flight modes maintaining full span ailerons throughout.

Thoughts .... All comments welcome
Dec 02, 2017, 01:14 AM
Registered User
IMHO crow has its use and its for steeper descents on a narrow ridge or even down a slope where its not flat. Use it like brakes on a race car brake hard before turns and off while turning. I tend to use it more than others and I also tend to land better than most. Better to use flaps on longer flat areas.
Dec 05, 2017, 07:43 PM
Registered User

She Flies ....


Just a brief update, finally managed to maiden my new plane. Decided to keep the setup as simple as possible....

Three flight modes
1. Full span with reflex - fixed
2. Full span with camber - fixed
3. Full span in neutral - uncoupled as flaps descend - outboard ailerons

Only got one flight in and landed without engaging the flaps. My elevator compensation was way off, sending me into a very steep dive so it seemed safer to bring it in the old way.

It's my best flyer yet and I'm looking forward to tossing her again this weekend with adjusted elevator comp ....

Some video
Albatross Maiden flight (1 min 40 sec)


Crash
Dec 06, 2017, 02:00 PM
Registered User
I just suggest you make sure you still keep some aileron control while applying full crow: test aileron effectiveness with crow at height.
In those tricky slope landings with lots of turbulence not enough aileron control can be disastrous.
Regards
Dec 07, 2017, 06:14 PM
Registered User
Thanks for the suggestion to check my aileron authority with flaps deployed, it didn't even cross my mind. I just dropped them, went into a dive, retracted them, recovered and went back to flying. I have no idea how she handles flaps down. As Curdman suggested earlier, there's a learning curve out there to be explored and enjoyed.

I might consider landing on high rates if maneuverability seems compromised. Would it be worthwhile exploring the possibility of a mix that overrides my rate switch on flap deployment ...just a thought. Probably wait for the results from my next flight before working myself into a lather over the unknown.

Crash


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