micro vortex generators
Thread Starter
Joined: Feb 2008
Posts: 9
Likes: 0
From: West-side rulezzzz
micro vortex generators
Hello guys,
I operate a cessna 172 skyhawk for low level powerline inspections. So when I read about the micro vg kit from www.microaero.com , I was amazed by the advantages it offers planes flying a lot in the slow speed region. Which I do a lot doing steep turns at 70kts at about 200ft AGL following the powerlines.
The advantages look amazing:
* Lower Lift Off Speed
* Lower Stall Speeds
* Improved Controllability
* Improved Characteristics
* Improved Safety
* S.T.O.L. Benefits
* 1 Day Installation
But my question was about the disadvantages, I can't help thinking that nothing in life comes for free?
Can somebody tell me a bit more about the practical use of the micro vg's. Maybe somebody has experience flying with a c172 with the VG's installed? Does it increase fuel consumption and by how much? Does it reduce cruise speed? What are the caracteristics in an accelerated stall. Are there other effects caused by this kit that could affect flying in some way?
Thanks a lot for any response, I hope to be able to improve safety since we are low and slow and in sometimes very rugged terrain.
Cheers
I operate a cessna 172 skyhawk for low level powerline inspections. So when I read about the micro vg kit from www.microaero.com , I was amazed by the advantages it offers planes flying a lot in the slow speed region. Which I do a lot doing steep turns at 70kts at about 200ft AGL following the powerlines.
The advantages look amazing:
* Lower Lift Off Speed
* Lower Stall Speeds
* Improved Controllability
* Improved Characteristics
* Improved Safety
* S.T.O.L. Benefits
* 1 Day Installation
But my question was about the disadvantages, I can't help thinking that nothing in life comes for free?
Can somebody tell me a bit more about the practical use of the micro vg's. Maybe somebody has experience flying with a c172 with the VG's installed? Does it increase fuel consumption and by how much? Does it reduce cruise speed? What are the caracteristics in an accelerated stall. Are there other effects caused by this kit that could affect flying in some way?
Thanks a lot for any response, I hope to be able to improve safety since we are low and slow and in sometimes very rugged terrain.
Cheers
Moderator
Joined: Feb 2000
Aviation Qualifications: CPL
Posts: 14,480
Likes: 178
From: UK
Looking at those claims, which you've obviously pasted from the company's website, the validation doesn't seem all that clear. Since they're claiming an FAA STC to go with it, possibly you could do worse than ask for a copy of the STC and (since presumably there is one) associated POH amendment - that may give you some clues.
G
G
Joined: Dec 2001
Posts: 1,835
Likes: 3
From: Philadelphia PA
Downsides?
I would think that trying to wash the little monsters without beating up your hands or snagging the washing and drying clothes on them would be a challenge.
Also, not sure what the stall characteristics might be like when you finally do get a stall, especially if you're carving pretty hard at 70 KIAS.
How will you find out aside from flying something with these devices installed and seeing what the stall characteristics are...
Does your stall warning system get modified once the devices are on?
Does your stall warning system currently give you any warning on a high-pitch rate stall at 70 KIAS?
I would think that trying to wash the little monsters without beating up your hands or snagging the washing and drying clothes on them would be a challenge.
Also, not sure what the stall characteristics might be like when you finally do get a stall, especially if you're carving pretty hard at 70 KIAS.
How will you find out aside from flying something with these devices installed and seeing what the stall characteristics are...
Does your stall warning system get modified once the devices are on?
Does your stall warning system currently give you any warning on a high-pitch rate stall at 70 KIAS?
Guest
Posts: n/a
vortex generators on light aircraft
The fitment of VGs to a light aircraft will lower the 1G stall speed. How much? Given the range of speeds available, I would be surprised if the decrease was much more than approx 5 Kts IAS, but I stand to be corrected. However, if you approach to land at the lower speed the VGs permit, you often will find that a steeper approach is being flown then would be flown by the same model aircraft without VGs fitted. No real problem unless you carry out a missed approach at low altitude. As the power/weight ratio has not changed, and you will be closer to the 'backside' of the drag curve, it can be easy to get into an increasing drag situation with insufficient excess power to fly away and with insufficient altitude to trade for IAS. I personally don't like to see VGs on light aircraft that were not designed for them and I don't allow for any significant performance increase over the 'classic' aircraft if I do fly an aircraft that has been the subject of a STC for VGs. But that is a personal opinion. Be careful, though.
Thread Starter
Joined: Feb 2008
Posts: 9
Likes: 0
From: West-side rulezzzz
Thanks for your responce.
One negative point about the insallation of VG's , I was told, is that once you "tamper" with the fusselage one could have problems to keep a plane in a life extension maintenace program.
Whether this is true or not I don't know I'm investigating this.
I also was told that for a C172 stall speed would only go down by a few knots but that aileron responce on slow speeds does improve a lot.
The same for the elevator, but this is not always an advantage, because due to the increased response one would be able to pull the plane into a deeper stall instead of the easy to recover stall the C172 usually has.
Anyway I'm still looking for info on it if I find more I will post it.
Greets
One negative point about the insallation of VG's , I was told, is that once you "tamper" with the fusselage one could have problems to keep a plane in a life extension maintenace program.
Whether this is true or not I don't know I'm investigating this.
I also was told that for a C172 stall speed would only go down by a few knots but that aileron responce on slow speeds does improve a lot.
The same for the elevator, but this is not always an advantage, because due to the increased response one would be able to pull the plane into a deeper stall instead of the easy to recover stall the C172 usually has.
Anyway I'm still looking for info on it if I find more I will post it.
Greets
Guest
Posts: n/a
stall speed
A 'certification' stall, i.e. an IAS decrease at the rate of 1kt/sec as opposed to a 'training' stall where level flight is maintained until the manifestation of the stall, will produce two different cockpit ASI readings for the two stalls. It is some time since I have flown a C172 but I imagine that the ASI does not indicate much below 30kts? If this is the case, an accelerated entry into the stall, not an 'accelerated stall' but a decrease in IAS of >1kt/sec may result in an unreadable IAS indication before the 'stall' IAS is reached. Particularly if the the VGs have lowered the stall CAS/IAS by, as you say, 'a few knots'. Tailplane control surface effectiveness is dependant on Reynolds number amongst other things but also energy recovery from the airflow off the wings and the propellor. Lower speed, less energy recovery, less effective the tail surfaces. Hence the 'mushy' controls.
Joined: Dec 2005
Posts: 178
Likes: 7
From: Perth
G,day Pilotpeter,
I did 2 seasons on the power lines for both Vic. and SA. back in the mid 90's
On the South Australian contract I flew a Robertson STOL kitted 172 and it was excellent. Flying into a slight head on breeze you could see a GS of 55 kts and thus give the observer a good look at the conductor, trees and tee's etc. and felt safe, guess indicated would've been around 65 kts. Probably need 70 to 75 in a non kitted version to feel comfortable, both with 1 stage flap.
Haven't flown VG's on a Cessna but from experience on others (mostly a pair of AT301's one with and one with out. I guess a 172 would gain about 5 kts at the low end and shed 1 or 2 kts at the top end. Your comment on improved aileron control is pretty true.
A bugger to wash though as Shawn pointed out. And if you do knock one or two off when cleaning it may mean you legally can't fly until fixed. Check that out yourself though.
Not unusual that when separation does occur it can be a little more pronounced. But this may well be type specific.
Neither company I flew for would condone steep turns at 70 kts, of course it can be done safely in the right hands, but how much extra money do you or the company make by reducing margins. The Vic's lost a crew in 95 to what appeared as stall incipient spin accident, and in the hands of respected pilot.
Your biggest asset for low speed flight will be a good set of hands with matching feet
Smooth as she goes and all that and know what the wind is doing. These won't cost the company a cent and they last and last and even get better with age.
M
I did 2 seasons on the power lines for both Vic. and SA. back in the mid 90's
On the South Australian contract I flew a Robertson STOL kitted 172 and it was excellent. Flying into a slight head on breeze you could see a GS of 55 kts and thus give the observer a good look at the conductor, trees and tee's etc. and felt safe, guess indicated would've been around 65 kts. Probably need 70 to 75 in a non kitted version to feel comfortable, both with 1 stage flap.
Haven't flown VG's on a Cessna but from experience on others (mostly a pair of AT301's one with and one with out. I guess a 172 would gain about 5 kts at the low end and shed 1 or 2 kts at the top end. Your comment on improved aileron control is pretty true.
A bugger to wash though as Shawn pointed out. And if you do knock one or two off when cleaning it may mean you legally can't fly until fixed. Check that out yourself though.
Not unusual that when separation does occur it can be a little more pronounced. But this may well be type specific.
Neither company I flew for would condone steep turns at 70 kts, of course it can be done safely in the right hands, but how much extra money do you or the company make by reducing margins. The Vic's lost a crew in 95 to what appeared as stall incipient spin accident, and in the hands of respected pilot.
Your biggest asset for low speed flight will be a good set of hands with matching feet
Smooth as she goes and all that and know what the wind is doing. These won't cost the company a cent and they last and last and even get better with age.M
Joined: Jan 2003
Posts: 1,479
Likes: 0
From: Surrey Hills
One thing I do notice is that all those competition slow flying Piper Cubs seem to fit the VG devices. I guess if you get used to hanging on the prop at a high angle of attack then to have them fitted is a plus in terms of controllability.
http://www.microaero.com/pages/a_jb-j3wh.html
They are placed in front of the rudder and ailerons in some set-ups.
http://www.americasflyways.com/feb05story.html
A number of Twin owners swear by them.
http://www.microaero.com/pages/v_testimonials.html
http://www.microaero.com/pages/a_jb-j3wh.html
They are placed in front of the rudder and ailerons in some set-ups.
http://www.americasflyways.com/feb05story.html
A number of Twin owners swear by them.
http://www.microaero.com/pages/v_testimonials.html
Joined: Mar 2008
Posts: 71
Likes: 0
From: USA
I'd be very surprised to see a 5 kt reduction in stall speed from those VGs. One of the programs I was working on was looking at a micro VG solution to a separation problem with the flaps fully extended. It helped a bit in terms of vibration and roll control, but did nothing to the stall speed. In the end, the idea was scrapped as not worth the trouble.
