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Strange "thingy" On A Cessna 206  
User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Posted (10 years 3 months 3 weeks ago) and read 5946 times:

Hey guys,

Was looking at a 1966 Cessna TU206B earlier today. Noticed under the starboard wing leading edge, a few feet out from the cabin, a small (~1.5 inch) tab sticking out of the bottom of the wing that looked like it could be blown back by wind. Does anyone know what this is? Not even the pilot knew...

It was not a stall warning sensor, although it was the same kind of idea.

37 replies: All unread, showing first 25:
 
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 1, posted (10 years 3 months 2 weeks 6 days 23 hours ago) and read 5871 times:

Well, my first guess was the stall vain, but you said no.....So maybe the HOBBS meter sensor..? I think some aircraft have this to tell the HOBBS meter when to start counting.


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 3 months 2 weeks 6 days 21 hours ago) and read 5798 times:

Its an air switch. Its used on airplanes that don't have Weight on Wheels (WOW) switches, also known as squat switches. This is typically the case in light aircraft.

They are used to signal various equipment that the airplane is airborne. Everything from Hobbs meters (total hours) or flight timers, or even avionics systems like TCAS or Wx Radar.

TCAS needs to know when the airplane is on the ground to know when to inhibit RAs. Weather radar can sometimes be tied to the air switch to inhibit ground operation.

I'm not suggesting that TCAS or Wx Radar is common in light aircraft, but I've seen such installations.

The last time I saw an air switch was on a Cessna 208 Caravan on amphib floats. It had a Honeywell IHAS system that incorporates TCAS and TAWS. It needs the signal to inhibit alerts while on the ground.





User currently offlineLiamksa From Australia, joined Oct 2001, 308 posts, RR: 0
Reply 3, posted (10 years 3 months 2 weeks 6 days 20 hours ago) and read 5766 times:

Our 172s have both an engine and flight switch. As far as I know the engine hours start ticking with the rise in oil pressure but I don't know about the flight hours.

EMBQA, Airplay, anyone.... How does the "air switch" work - the pressure distribution around the wing? Airspeed? Our aircraft don't have the feature described in the first post so where is it usually incorporated?

(I'm leaning towards a simple airspeed switch as i'd imagine that most systems are similar but installed in various places)

Cheers  Wink/being sarcastic



User currently offlineRalgha From United States of America, joined Nov 1999, 1614 posts, RR: 6
Reply 4, posted (10 years 3 months 2 weeks 6 days 20 hours ago) and read 5749 times:

The ones I've seen are simply a small metal flap that hangs down off the wing. When the wind blows (i.e. the airplane moves forward at some sort of substantial speed), the little flap is pushed back and closes a switch.


09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
User currently offlineFlightSimFreak From United States of America, joined Oct 2000, 720 posts, RR: 0
Reply 5, posted (10 years 3 months 2 weeks 6 days 19 hours ago) and read 5718 times:

In the planes I fly, the garmins recognise a groundspeed greater than 30 knots as being airborne.

User currently offlineL-188 From United States of America, joined Jul 1999, 29800 posts, RR: 58
Reply 6, posted (10 years 3 months 2 weeks 6 days 18 hours ago) and read 5708 times:

The only tab like that on Cessna wings that I know of is the electric stall horn.

And starboard side leading edge is where I remember it being, pretty univerally on all Cessna singles.

I don't think any have used reeds since the C-195



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineDufo From Slovenia, joined May 1999, 798 posts, RR: 4
Reply 7, posted (10 years 3 months 2 weeks 6 days 16 hours ago) and read 5679 times:



This?



I seriously think I just creamed my pants without any influence from any outside variables.
User currently offlineL-188 From United States of America, joined Jul 1999, 29800 posts, RR: 58
Reply 8, posted (10 years 3 months 2 weeks 6 days 16 hours ago) and read 5674 times:

Sure looks like a stall horn switch to me.


OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 9, posted (10 years 3 months 2 weeks 6 days 4 hours ago) and read 5582 times:

Yep, it looks like a stall horn switch, but thats not what it is. Imagine what is in that image, only on the bottom of the wing (a few inches back from the leading edge) instead of the front of the wing, hanging straight down. It had the ability to be blown backwards. Sounds like it is an airborne switch, but what would this be used for on a 206?

User currently offlineFly727 From Mexico, joined Jul 2003, 1789 posts, RR: 19
Reply 10, posted (10 years 3 months 2 weeks 6 days 2 hours ago) and read 5564 times:

Might sound ridiculous but I think...

Some of the pitot tubes have a little lid that when the aircraft is on the ground at low speeds it remains over the hole protecting it from insects, water, etc. When the aircraft speeds up it retracts due to the wind keeping the hole free to receive the impact pressure it needs.

That's what I think it is...

RM  Smile



There are no stupid questions... just stupid people!
User currently offlineBlackbird1331 From United States of America, joined Apr 2004, 1893 posts, RR: 0
Reply 11, posted (10 years 3 months 2 weeks 6 days 1 hour ago) and read 5546 times:

I think it is just a thingy waiting for someone to ask, "what are you doing here?" And the reply is, "waiting for you to go take some flying lessons."


Cameras shoot pictures. Guns shoot people. They have the guns.
User currently offlineRalgha From United States of America, joined Nov 1999, 1614 posts, RR: 6
Reply 12, posted (10 years 3 months 2 weeks 6 days ago) and read 5542 times:

No, it's not a flap covering the pitot tube. It is not a stall warning vane. Read Flyf15's description for crying out loud.

As someone said before, it is an airborne switch, probably used to start a meter in the airplane. Some places bill based on actual flight time, not engine operation time like a standard hobbs meter measures. An airborne switch such as this would be necessary for such billing procedures.



09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 13, posted (10 years 3 months 2 weeks 5 days 23 hours ago) and read 5533 times:

The only tab like that on Cessna wings that I know of is the electric stall horn.

And starboard side leading edge is where I remember it being, pretty univerally on all Cessna singles.


Many single engine Cessnas like 150/172/177/180/185 made after the 195 use reed switches for stall warning therefore all you would see on the leading edge is a screened port.

As a matter of fact, there is an AD out that makes the operator pre-flight the system by sucking on the screened port to verify operation.

The description in the original post pretty much narrows it down to an airspeed switch. To clarify, airspeed switches aren't normally installed at build and are not installed on the leading edge like stall vanes. They are typically installed after-market. They usually consist of a microswitch and a length of aluminum about 2 or 3 inches long that hangs straight down off the bottom of the wing that hinges back when air forces it back, activating the switch.





User currently offlineL-188 From United States of America, joined Jul 1999, 29800 posts, RR: 58
Reply 14, posted (10 years 3 months 2 weeks 5 days 21 hours ago) and read 5506 times:

So in other words, put a little bit of bubble gum on the switch to hold it in place and you get to fly for free?


OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineLiamksa From Australia, joined Oct 2001, 308 posts, RR: 0
Reply 15, posted (10 years 3 months 2 weeks 5 days 20 hours ago) and read 5496 times:

And starboard side leading edge is where I remember it being, pretty univerally on all Cessna singles.

Port?  Big grin

Just for interest's sake (not saying that's what it is...) some aircraft utilise 2 stall warning tabs at different angles as a result of the different stalling attitudes which correspond to various flap settings...

So in other words, put a little bit of bubble gum on the switch to hold it in place and you get to fly for free?

You'd think they'd use engine hours or some other system. I once read about a flight switch which started counting with gear retraction. This switch was used to calculate the cost of the flight and not surprisingly a few people just flew around with the wheels hanging out.


User currently offlineAirtractor From Canada, joined Apr 2004, 26 posts, RR: 0
Reply 16, posted (10 years 3 months 2 weeks 5 days 13 hours ago) and read 5457 times:

I think I know what it is, There is a similar device on our spray planes, always on the right hand wing, outside the propwash area. It is a angle of attack indicator switch for monitoring wing loading. I have seen them on float planes before so it may be the same thing.


Cheers

Kev.



In memory of Agnes & Aaron, you're always with me when I fly.
User currently offlineMD-90 From United States of America, joined Jan 2000, 8507 posts, RR: 12
Reply 17, posted (10 years 3 months 2 weeks 2 days 16 hours ago) and read 5307 times:

Airtractor said exactly what I was thinking.

But AOA gauges generally stick out in front of the leading edge about a foot or a little more. Well, at least the ones I've read about that are homemade and installed on experimentals and kitbuilt aircraft. Usually, on the end of the pole they have a flat metal plate (vertical) with a diagram on it, and a horizontal metal vane that manually points to the AOA (as you can guess, this isn't terribly precise, but it works).

Usually they're out in front of the wing. BUT, a certified version (which a 206 would have to have), with a display in the cockpit could be exactly what Flyf15 is describing.

I agree with Airtractor. I think it's an AOA instrument.


User currently offlineCanoecarrier From United States of America, joined Feb 2004, 2839 posts, RR: 12
Reply 18, posted (10 years 3 months 2 weeks 2 days 14 hours ago) and read 5297 times:

L-188: LOL I wish I knew that trick when I was learning to fly! To think of how many airplanes I wouldn't have had to wash or fuel had I known that.

Reminds me of a commercial:
Flight instructor.....$20/hour
Good Plane...........$50/hour

Remembering to bring your chewing gum....Priceless!

It's been a while since I've done some flight instruction so please don't critique the prices.



The beatings will continue until morale improves
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 19, posted (10 years 3 months 2 weeks 2 days 14 hours ago) and read 5293 times:

Where do you stick a piece of chewing gum on the instructor to stop those hours from counting?  Smile

Cheers,
Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 20, posted (10 years 3 months 2 weeks 2 days 12 hours ago) and read 5282 times:

Usually they're out in front of the wing. BUT, a certified version (which a 206 would have to have), with a display in the cockpit could be exactly what Flyf15 is describing.

I agree with Airtractor. I think it's an AOA instrument.


Why would somebody pay to install an AOA indication system on a C206?


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 21, posted (10 years 3 months 2 weeks 2 days 11 hours ago) and read 5259 times:

We’re not talking something that’ll give the AoA in degrees here. We’re talking about a device which will indicate when the AoA goes above the comfortable margin to the stall (critical AoA) through setting off a horn. Pretty useful.

As for having a real AoA indicator, it would definitely be useful in just about any aircraft. You could forget half of the V speeds right away...

Cheers,
Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 22, posted (10 years 3 months 2 weeks 2 days 8 hours ago) and read 5235 times:

As for having a real AoA indicator, it would definitely be useful in just about any aircraft. You could forget half of the V speeds right away...

I was alluding to the cost of such systems. I've been involved in the installation of indicated AOA and know for the most part they aren't cheap.

Also, unless you are talking about relatively high performance airplanes or special ops, its hard to justify and a C206 doesn't typically fall into this category.

As far as a non indicating AOA warning system, this sounds an awful lot like a basic stall warning system, that C206s already have fitted.


User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 25
Reply 23, posted (10 years 3 months 2 weeks 2 days 4 hours ago) and read 5207 times:

Just to clarify, is this...

or

...the sort of thing you're talking about, with this sort of aural warning? I think they cost around US$800 to $1200, probably a useful investment. I suppose for aircraft like the C206 it isn't really necessary, though...

Cheers,
QantasA332


User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 24, posted (10 years 3 months 2 weeks 1 day 12 hours ago) and read 5149 times:

QuantasA332,

I should have known somebody was going to bring this PSS system up...

That particular system doesn't use an AOA vane. It relies on pressure sensors on the top and bottom of the wing to determine pressure differences. It is not a true AOA sensing system, and is therefore not approvable as such.

They currently have installations on RV-6 and Lancair machines. Certification programs for additional aircraft are not planned. This is truely a "toy" for "toy" airplanes.


25 Airtractor : Airplay, If you have ever flown an aircraft loaded to gross, on a hot day, at slower than normal cruise speeds and low to the ground. You will surely
26 PPGMD : Though it might be an AoA indicator, I doubt it at least not in a C206. I believe it's a switch to indicate flight hours, most FBOs do the 100 hour ma
27 Post contains images Airplay : And as for cost, the system on my AT-501 cost about $2500.00, cheap insurance for a $300,000.00 turbo-prop spray plane. I can't tell you enough how mu
28 L-188 : Also, unless you are talking about relatively high performance airplanes or special ops, its hard to justify and a C206 doesn't typically fall into th
29 Airplay : I dunno, 2500 is not actually that expensive when you compare it to the costs of some of the avionics that are out there. Man, you guys really have to
30 Post contains images L-188 : Sorry man, been hanging around Lears 25/35's and Metro's for too long. It rots the brain
31 Post contains images Airplay : Sorry man, been hanging around Lears 25/35's and Metro's for too long. You poor b*stard! [Edited 2004-06-12 16:31:22]
32 MD-90 : "toy" airplanes. Only ignorance can explain someone who would call a Lancair a toy. The Lancair IV-P is the highest performance piston single-engine a
33 Airplay : Only ignorance can explain someone who would call a Lancair a toy. The Lancair IV-P is the highest performance piston single-engine aircraft ever buil
34 L-188 : The Lancair IV-P is the highest performance piston single-engine aircraft ever built. Friends don't let Friends Fly FIBERGLASS!!!
35 MD-90 : Yeah, that's why the IV is made from CARBON FIBER. There's a little fiberglass in the vertical tail, I believe. It's there for the embedded antennas,
36 Airplay : Airplay, surely you understood that I meant to the SAFE limits. Not literally at one degree below the AOA at which the wing will stall. OK...and what
37 Post contains images PPGMD : Friends don't let Friends Fly FIBERGLASS!!! I will have to tell that to everyone on the glider field, since it appears that glass is all the rage.
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