flyf15
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Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 10:08 am

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.
 
EMBQA
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 11:26 am

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"
 
airplay
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 1:24 pm

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.



 
liamksa
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 1:59 pm

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

 
Ralgha
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 2:16 pm

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.
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flightsimfreak
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 3:33 pm

In the planes I fly, the garmins recognise a groundspeed greater than 30 knots as being airborne.
 
L-188
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 3:52 pm

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.
 
Dufo
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 6:07 pm



This?
I seriously think I just creamed my pants without any influence from any outside variables.
 
L-188
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RE: Strange "thingy" On A Cessna 206

Sun Jun 06, 2004 6:09 pm

Sure looks like a stall horn switch to me.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
flyf15
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 6:08 am

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?
 
fly727
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 8:10 am

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!
 
Blackbird1331
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 9:23 am

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.
 
Ralgha
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 9:59 am

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
 
airplay
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 10:51 am

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.



 
L-188
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 1:31 pm

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.
 
liamksa
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 2:42 pm

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.
 
Airtractor
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RE: Strange "thingy" On A Cessna 206

Mon Jun 07, 2004 9:13 pm

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.
 
MD-90
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RE: Strange "thingy" On A Cessna 206

Thu Jun 10, 2004 6:21 pm

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.
 
canoecarrier
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RE: Strange "thingy" On A Cessna 206

Thu Jun 10, 2004 8:05 pm

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
 
FredT
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RE: Strange "thingy" On A Cessna 206

Thu Jun 10, 2004 8:11 pm

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.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Thu Jun 10, 2004 9:59 pm

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?
 
FredT
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RE: Strange "thingy" On A Cessna 206

Thu Jun 10, 2004 11:32 pm

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.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Fri Jun 11, 2004 2:09 am

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.
 
QantasA332
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RE: Strange "thingy" On A Cessna 206

Fri Jun 11, 2004 6:45 am

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
 
airplay
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RE: Strange "thingy" On A Cessna 206

Fri Jun 11, 2004 10:30 pm

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.
 
Airtractor
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 6:47 am

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 appreciate a AOA indicator on the panel. 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 much I rely on it during spraying operations.

Cheers

Kev.
In memory of Agnes & Aaron, you're always with me when I fly.
 
PPGMD
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 8:13 am

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 maintenance when the hobbs meter reads 100 hours, but in the FARs (as a mechanic who had one of these on this airplane pointed out for me once) it says that it only has to be done every 100 flight hours. So FBOs that wish to squeeze every dime they can, install a switch (often calibrated to the flaps down stall speed) that that will turn on another hobbs meter that records the flight hours.

The person that I knew that did this used a squat switch in the retractable gear aircraft that he owned.

QantasA332,

I am familiar with both of those AoA meters, they both use a pressure sensing method to determine the AoA. They will look like a little static port on the wing. They are pretty cheap because they don't require the vane that most AoA meters use. Also I don't believe that they have an STC for certified aircraft. Which a C206 is.

Airplay,

Toy airplane? I am hurt, I have recorded my fastest PIC ground speed ever in one of the aircraft you call a toy. Those toys will kill you just as fast as the certified suckers. *wink*
At worst, you screw up and die.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 10:11 am

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 much I rely on it during spraying operations.


Airtractor , I stated earlier:

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.

Your AT-501 aircraft in spray operations falls into the category of high performance special ops. I am well aware that AOA indication is common and invaluable in spray aircraft.

Just out of curiosity, what type of indicated AOA system do you have installed? Does the $2500 include the price of a replacement indicator or the entire system new, installed and certified?

Toy airplane? I am hurt, I have recorded my fastest PIC ground speed ever in one of the aircraft you call a toy. Those toys will kill you just as fast as the certified suckers. *wink*

Yah...right after I wrote that I figured I would hear from and RV-6 or Lancair enthusiasts!  Smile

I unfairly equated non-certified airplanes with the word "toy". You are right PPGMD, a non-certified airplane can kill you just as fast as a certified one. I don't get involved with those types at all but I do know alot of equipment finds itself on board without the scrutiny that "certified" airplanes are subject to. Thats what I was alluding to.


 
L-188
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 2:34 pm

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

I dunno, 2500 is not actually that expensive when you compare it to the costs of some of the avionics that are out there.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 10:42 pm

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 start reading and understanding the entire posts or we'll be on this topic all year....

First of all, in case you didn't pick up on it L-188, I highly doubt you'll end up with an installed and certified indicated AOA system on your C206 for $2500.

If it was that easy, don't you think you'd see more of them in light aircraft? It just isn't important to have instantaneous AOA indication in a C206 in the role they typically take. I highly doubt you'd be able to find many accidents in a C206 that may have been avoided had the pilot had such a system.

Interestingly, most high performance aircraft are not fitted with AOA indicators. Some, like the Astra SPX (I think its called the Gulfstream 100 now) don't even have an active stall warning system because it provides adequate aerodynamic feedback (pre-stall buffet).

Now Learjets are a different story. The 2X/3X series especially. Those things are bricks at low speed.





 
L-188
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 11:08 pm

Sorry man, been hanging around Lears 25/35's and Metro's for too long.

It rots the brain  Nuts

OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Sat Jun 12, 2004 11:30 pm

Sorry man, been hanging around Lears 25/35's and Metro's for too long.

You poor b*stard!

 Smile

[Edited 2004-06-12 16:31:22]
 
MD-90
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RE: Strange "thingy" On A Cessna 206

Fri Jun 18, 2004 9:47 pm

"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 aircraft ever built.


If it was that easy, don't you think you'd see more of them in light aircraft?

Actually, there are quite a few on very simple aircraft, like the mutltitude of Quicksilvers.

Since an aircraft doesn't stall due to airspeed, but only the angle of attack of the wing relative to the airflow, yes, AOA indicators are valid pieces of equipment even for a Cessna 206. They allow you to fly the aircraft right to the limits with full confidence that it will not stall/spin/kill you.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Fri Jun 18, 2004 10:22 pm

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 built.

Oh please....only an internet troll with flamebait intentions would bring the word "ignorance" into this discussion especially after I explained my comments once already.

Most here understand that my reference to "toy" was not indicitive of the performance of the airplane. It was in reference to Lanair's non-certified status of the kit line. And I stated that.

For better or worse, you can pretty much do what you want on the uncertified kit planes without oversight of the regulator. So lots of junk finds its way into these cockpits. Furthermore, I was making reference to the Lancair line's utility. You certainly won't (ever) see a Lancair IV-P in commercial service. Thus it is a truly recreational aircraft and fits the "toy" category quite well when compared to a C206.

Actually, there are quite a few on very simple aircraft, like the mutltitude of Quicksilvers.

Another "toy" that enjoys even less utility than Lancairs.

Since an aircraft doesn't stall due to airspeed, but only the angle of attack of the wing relative to the airflow, yes, AOA indicators are valid pieces of equipment even for a Cessna 206. They allow you to fly the aircraft right to the limits with full confidence that it will not stall/spin/kill you.

Valid? What does that mean exactly? Usefull? Required? Pretty much anything can be installed on any airplane. That doesn't automatically make it a practical device.

TCAS is "valid" and so is TAWS and weather radar. But will you typically see that stuff on a Quicksilver, Lancair or Cessna 206? Umm...no.

And with respect to flying the aircraft "right to the limits", Bad advice. I would certainly hope that the majority of private pilots would NOT consider an indicated AOA system license to do that. Fly the airplane within the published approved limitations using the AOA indicator as a warning system and you will stay out of trouble. Conduct performance takeoffs using an AOA indicator pegged on the outer limits of the green arc, and you will crash one day....





 
L-188
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RE: Strange "thingy" On A Cessna 206

Fri Jun 18, 2004 11:02 pm

The Lancair IV-P is the highest performance piston single-engine aircraft ever built.

Friends don't let Friends Fly FIBERGLASS!!!
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
MD-90
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RE: Strange "thingy" On A Cessna 206

Sat Jun 19, 2004 1:46 am

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, since antennas and carbon fiber don't mix so well.


You certainly won't (ever) see a Lancair IV-P in commercial service.

No, you won't. But there are many professionals who do use experimental aircraft for their business. Contractors, doctors, engineers, etc. They just don't fly pax.



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.
 
airplay
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RE: Strange "thingy" On A Cessna 206

Sat Jun 19, 2004 3:25 am

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 exactly are the "safe" limits and how would a pilot determine that exactly? 2 degrees below stall? 3 degrees?

You determine that by using the design and certification methods prescribed by the civil airworthiness authority, and most probably verified by flight test....which as an owner of a Lancair non-certified kit is under no obligation to do. Is that clearer?

So the "SAFE" thing to do, is fly the airplane in accordance with the published airworthiness limitations and the normal procedures and use the AOA as a warning device. Period.
 
PPGMD
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RE: Strange "thingy" On A Cessna 206

Mon Jun 21, 2004 3:52 am

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.  Big grin
At worst, you screw up and die.

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