Ted
The pilot formerly known as Twin Engine Ted
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iFlyNothing
It continues to amaze me how many people seem to consciously wake up and decide... "I want to be an NTSB report today."
204 knots
- Thread starter Jay Honeck
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It continues to amaze me how many people seem to consciously wake up and decide... "I want to be an NTSB report today."
Skylane81E
Final Approach
Yep, I'd take the "it has done it" to mean that I have a safety margin and abide by VNE
Skylane81E
Final Approach
I will also admit however that when I first learned that VMC is true airspeed and realized I'd been 32kts over that number before I thanked the aviation gods and intend not to do it again.
Ted -- Can you explain this a little more? I'm having trouble understanding how TAS (vs. IAS) matters with respect to Vne.
Thanks!
dell30rb
Final Approach
You mean Vne? I'm assuming you are talking about a 182 or similar
Vne is listed as indicated airspeed in most limitations. As I mentioned earlier most N/A airplanes do not list a true airspeed value that is not to be exceeded. (although I am sure it has been calculated)
What Ted said is more like an easy rule of thumb so you never get yourself in trouble. However below the oxygen altitudes, if you go up to your Vne in IAS the TAS won't be above any critical value.
Jay Honeck
Touchdown! Greaser!
Yeah, I've seen the YouTube videos. It's amazing how quickly flutter can tear the tail off.
It makes me wonder how the RV-10 can have a higher Vne than the RV-8? One is a load hauler, while the other is a dart. Why would the -10's Vne be 25+ knots faster than the -8's?
GEICO? Is the -10 built that much beefier? I've seen them both under construction, and they didn't look any different, to my untrained eye.
dell30rb
Final Approach
Like I mentioned, flutter resistance is not simple to calculate because it hinges on a ton of different variables. Shape/Type of the airfoil, balance of the control surfaces, rigging of the plane, rigidity and strength of wings/elevator all come into play.
Jay Honeck
Touchdown! Greaser!
Yep. I'm just wondering what Van did to the -10 to increase Vne by over 10%, as compared to the -8 series. That's a significant difference.
dell30rb
Final Approach
There are two things to be worried about when flying at high speeds. Pressure of the air on things can cause them to break and rip off (think windscreen, fairings). The other concern is flutter. Flutter is when the airfoils become unstable and will literally start oscillating uncontrollably (think flag in the breeze).
We know that indicated airspeed is essentially a measure of the force of the air being rammed down that pitot tube. As you climb, the force is reduced for the same TAS. Thats why your ASI could indicate 100 but your groundspeed on a no wind day might be 120 knots up at altitude.
The issue with things breaking off is a function of the force so it relates closely to indicated airspeed.
The flutter phenomenon is related to TAS only. So you could be flying your turbocharged airplane in the thin air at 25,000 feet with your IAS under the Vne limit of 200 knots, but your TAS (remember groundspeed matches TAS if no wind day) is through the roof and high enough that flutter could be encountered.
Ted
The pilot formerly known as Twin Engine Ted
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iFlyNothing
Basically you have a number of different factors that limit how fast you can go. Structurally something can fall off, aerodynamically airfoil can stop working right, and then aerodynamics can lead to flutter which can cause tails to fall off.
Now, they all kick in at different points. So for example in the Commander 690A, Vne was something like 240-245 KIAS. We cruised at 270 KTAS at altitude. The barber pole was about 20 KIAS faster than we were going (I want to say around 160 indicated? So theoretically we could do faster in a dive without exceeding a flutter concern.
You, Jay, and I don't have barber poles in our planes. So where is the flutter limit? I don't know, and I don't want to find out. On the Commander, someone smarter than me determined it. On the 310 someone smarter than me determined Vne. So if you use Vne as a TAS limit as well, you'll be safe.
Thanks Ren and Ted. Would it be fair to say that flutter somehow related to intertia? I'm trying to wrap my head around "forces" which would be different from the ones resulting just from airflow.
Sam (who got poor grades in high school physics)
Sam (who got poor grades in high school physics)
JHW
En-Route
If you want to relate it something you can "see" then in greatly simplified terms think of flutter as being driven by vortex shedding. To make it visible, the eddy's you see circling behind a rock in a stream are a function of the stream's speed. On an airplane control surface the vortex shedding is a function of the velocity of the molecules over the surface (true air speed) and has nothing to do with static pressure due to flow being stopped by a blunt object (indicated air speed)
jesse
Touchdown! Greaser!
I read an article about a military fighter pilot not too long ago in a normally aspirated RV-4 that was up high and I think was doing a spiraling descent through a hole in the clouds or something (don't remember the specifics) and experienced some pretty dramatic flutter. His TAS was much higher than Vne.
That said, I still want a RV-4. You just have to use your head, like in anything.
Call me paranoid but there is no way in hell I'd attach something to my Flybaby with nothing but rtv. Is that a method others are using to attach that fairing?
That said, I still want a RV-4. You just have to use your head, like in anything.
Call me paranoid but there is no way in hell I'd attach something to my Flybaby with nothing but rtv. Is that a method others are using to attach that fairing?
jesse
Touchdown! Greaser!
Airplanes ride on air, reduce the density of the air, and it's going to take more of it to get the job done.
dell30rb
Final Approach
Sea level: 120 knots IAS and 120 knots TAS
10,000 feet 100kts indicated, 120 knots TAS
Say you stick your hand out the window. At sea level, there will be more pressure pushing your hand back. At 10,000 feet, there will be less pressure pushing your hand back. But in each case, the molecules are moving over your hand at the same speed. It just feels lighter at altitude, because the air is less dense.
This pressure felt by your hand is what the airfoils have to work with in terms of generating lift. But the speed of the molecules (which you don't feel) is what affects the potential for flutter.
Compare water to air. Stick your hand in the air off of a boat doing 10mph. Then stick it in the water (water is much more dense than air). In the water your arm is about to get ripped off, but in each scenario the molecules of air and water are moving over your hand at 10mph.
10,000 feet 100kts indicated, 120 knots TAS
Say you stick your hand out the window. At sea level, there will be more pressure pushing your hand back. At 10,000 feet, there will be less pressure pushing your hand back. But in each case, the molecules are moving over your hand at the same speed. It just feels lighter at altitude, because the air is less dense.
This pressure felt by your hand is what the airfoils have to work with in terms of generating lift. But the speed of the molecules (which you don't feel) is what affects the potential for flutter.
Compare water to air. Stick your hand in the air off of a boat doing 10mph. Then stick it in the water (water is much more dense than air). In the water your arm is about to get ripped off, but in each scenario the molecules of air and water are moving over your hand at 10mph.
dell30rb
Final Approach
Some of the silicone adhesives I have worked with on boats would definitely do the job!
JHW
En-Route
velocity of molecules is not "due to TAS" rather it IS TAS. Flutter has nothing to do with lift and vice-versa. An antenna can experience flutter.
bnt83
Final Approach
Exactly.
RTV is all fine and dandy or that sheel metal screw that doesn't quite fit will be fine right? Right up until a Lear 60 drives over and blows a tire hitting what falls off YOUR airplane and kills everyone onboard.
Don't be stupid about loose parts on your airplanes folks.
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moonshine
Line Up and Wait
I think that guy was just in a gradual descent, from what I remember from that article. It did have to do with TAS, as you said.
I have seen an elevator off of a Rocket that suffered in flutter - very scary. It had that pronounced wave shape. I've been told that the pilot went exploring Vne, got into severe elevator flutter and what saved him was one of the elevators failed and was stuck perpendicular to the airflow, slowing the airplane down.
No idea why anyone would RTV stuff to their airplane. I mean, there's a reason they invented JB Weld, you know
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jsstevens
RotorAndWing
Final Approach
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Rotor&Wing
Airframe stress is cumulative. You can get away with it maybe once, maybe several times, but one day it won't work.
Yep.
Ain't that the truth!
RotorAndWing
Final Approach
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Rotor&Wing
Exactly.
RTV is all fine and dandy or that sheel metal screw that doesn't quite fit will be fine right? Right up until a Lear 60 drives over and blows a tire hitting what falls off YOUR airplane and kills everyone onboard.
Don't be stupid about loose parts on your airplanes folks.
Never ceases to amaze me the "creative" ways some try to maintain their aircraft.
JoeSelch
Pattern Altitude
I have a mental list of a Smoking Holes To Be ... maybe it's time to start writing them down
Ted
The pilot formerly known as Twin Engine Ted
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iFlyNothing
I had suggested getting a pool going.
Skylane81E
Final Approach
Yeah, my iPad knows VMC, guess it didn't know VNE, as I just had to teach it now.
And I was at O2 levels, well into the yellow, whoops
JHW
En-Route
you can find all sorts of videos of flutter on youtube. This is one of my favorites because it's a plane we are all familiar with, not some unobtanium military experiment.
http://www.youtube.com/watch?v=pEOmCkZyXzk
http://www.youtube.com/watch?v=pEOmCkZyXzk
dell30rb
Final Approach
Yeah, good idea to avoid that.
Funny thing about flutter is that it usually takes some upset for it to get going. Sometimes airplanes can fly way past their Vne (TAS) and never get it.
IIRC test pilots will fly the planes up to the calculated TAS and then give the controls quick jabs and bumps to see if they can initiate flutter.
poadeleted21
Touchdown! Greaser!
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or RTV silicone.
wabower
Touchdown! Greaser!
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Wayne
I decided years ago to use "buzz" rather than "flutter" to describe the event to students and young pilots, simply because that's what it looks like when you watch the videos that have since become available on the internet rather than only at safety meetings. During the follow-up discussions about the control surface departing the airplane nobody has opined that it looks more like a flutter.
Todd Copeland
Pre-takeoff checklist
IO540 lycoming, 16gph for that speed! But you cover a lot of ground fast so mpg isn't that bad.
bbchien
Touchdown! Greaser!
hey a no - a- kiddin..... RTV?
Never ceases to amaze me the "creative" ways some try to maintain their aircraft.
Jay, are you going to live long enough to survive to adulthood?
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JHW
En-Route
that's definitely a better description of what it feels like through the stick. But I don't think either word really conveys the full import.
JHW
En-Route
the redline "dive" is the part of test flying a new homebuilt that i hate most. There have been 2 where I felt a buzzing in the stick i thought might be a hint of flutter. One was a lancair, the other an aeronca-champ knock off. It can happen over the whole spectrum of planes and in this context you can usually trace it to some sloppy connection in a trim tab linkage or something along those lines. the aeronca-like had some creative tail mods that, once undone, flew fine. The lancair, the builder could never find a reason for it and i refused to fly it again.
Jay Honeck
Touchdown! Greaser!
Oh, Lord -- here we go again? Really?
Dow Corning RTV silicone adhesive -- the real stuff, not the crap you'd buy at Pep Boys -- will hold a fiberglass gear fairing on more securely than the four sheet metal screws most people use by a factor of ten.
In fact, it's basically permanent. If I ever want to remove it, I'm in for hours of careful cutting with a sharp blade and fishing line.
Jay Honeck
Touchdown! Greaser!
Ouch. I thought burning 12 GPH (in cruise; 23 GPH at takeoff power) sucked in my O-540-powered Pathfinder. Of course, I was hauling 5/8ths of a ton, while grunting along at just 140 knots.
Still, 230 knots in cruise is awesome. I can see owning a Glasair someday. Heck, the -8A's so small, a Glasair would fit right next to it in the hangar!
jesse
Touchdown! Greaser!
Which product of theirs exactly?
I've looked at pictures of many different RV's with upper wheel fairings. I've also looked at the installation manuals for RV upper wheel fairings. No one is attaching these things with RTV Jay, they are attaching them with screws.
bnt83
Final Approach
So, okay, I was in a slight descent, with a bit of a tailwind, but 185 knots indicated airspeed is still pretty healthy for a 180 HP homebuilt, IMHO.
This was our first flight in Amelia after installing the new upper main gear fairings, pictured below. For whatever reason, the original builder never got around to installing them, and the guy that we bought her from (who owned her for 7 years) never did, either.
As my first airframe mod, I think they cleaned up her looks quite nicely. I purchased the fairings pre-made, trimmed them to fit, painted them with rattle cans of primer/finish coat/clear coat, and stuck 'em on with RTV.
Yep, RTV. I didn't want to drill rivnuts for screws, cuz the wing spar is right around where I would want to drill. Since these fairings don't come off for the annual inspection, I opted to install them with RTV, which makes them more or less permanent. Naturally, I was very happy to see them still attached after hitting 235 mph.
Did the aerodynamic advantage of the fairings allow us to fly faster? Dunno, but they did clean up a pretty ugly area, aerodynamically. In the end, though, I just think they look nicer.
Ok? So there's nothing worth looking at in there?