How strong is the M20 wing?

[mooniac15u]

23.1545 Airspeed indicator.

(a) Each airspeed indicator must be marked as specified in paragraph (b ) of this section, with the marks located at the corresponding indicated airspeeds.

(b ) The following markings must be made:

(1) For the never-exceed speed V NE, a radial red line.

(2) For the caution range, a yellow arc extending from the red line specified in paragraph (b )(1) of this section to the upper limit of the green arc specified in paragraph (b )(3) of this section.

(3) For the normal operating range, a green arc with the lower limit at V S1 with maximum weight and with landing gear and wing flaps retracted, and the upper limit at the maximum structural cruising speed V NO established under § 23.1505(b ).

(4) For the flap operating range, a white arc with the lower limit at V S0 at the maximum weight, and the upper limit at the flaps-extended speed V FE established under § 23.1511.

(5) For reciprocating multiengine-powered airplanes of 6,000 pounds or less maximum weight, for the speed at which compliance has been shown with § 23.69(b ) relating to rate of climb at maximum weight and at sea level, a blue radial line.

(6) For reciprocating multiengine-powered airplanes of 6,000 pounds or less maximum weight, for the maximum value of minimum control speed, VMC, (one-engine-inoperative) determined under § 23.149(b ), a red radial line.

(c ) If V NE or V NO vary with altitude, there must be means to indicate to the pilot the appropriate limitations throughout the operating altitude range.

[PTK]

The red line is an IAS.

However the actual Vne is a TAS.

It's presentation to the pilot is aircraft dependent precisely because red line IAS decreases with altitude.

This is the reacon for c above.

[mooniac15u]

However the actual Vne is a TAS.

 

 

Incorrect.  The formula for calculating Vne is laid out in Part 23.  It is derived from other IAS measurements.

[Bob_Belville]

http://tailspinstales.blogspot.com/2009/11/vne-ias-tas-and-bvds.html

[PTK]

Incorrect. The formula for calculating Vne is laid out in Part 23. It is derived from other IAS measurements.

I respectfully disagree.

Vne is a TAS dependent figure. It is not an IAS figure as are stall and flap speeds for example.

[Shadrach]

The red line is an IAS.

However the actual Vne is a TAS.

It's presentation to the pilot is aircraft dependent precisely because red line IAS decreases with altitude.

This is the reacon for c above.

© is there for aircraft equipped with a barber pole on the ASI and it would be mandated in the TCDS. It would still be an indicated airspeed but one that gets adjusted by altitude.

Vne is not entirely based on flutter. It is based on a host of design limits, you are focused on one.

[PTK]

© is there for aircraft equipped with a barber pole on the ASI and it would be mandated in the TCDS. It would still be an indicated airspeed but one that gets adjusted by altitude.

Vne is not entirely based on flutter. It is based on a host of design limits, you are focused on one.

And it is adjusted by altitude because???

(Hint: the red line IAS that yields the Vne TAS, by definition, decreases with altitude!)

[mooniac15u]

I respectfully disagree.

Vne is a TAS dependent figure. It is not an IAS figure as are stall and flap speeds for example.

 

23.335Design airspeeds.

Except as provided in paragraph (a)(4) of this section, the selected design airspeeds are equivalent airspeeds (EAS).

 

 

Vne is defined in Part 23 1505:

(a) The never-exceed speed VNE must be established so that it is—

(1) Not less than 0.9 times the minimum value of VD allowed under § 23.335; and

(2) Not more than the lesser of—

(i) 0.9 VD established under § 23.335; or

(ii) 0.9 times the maximum speed shown under § 23.251.

 

Vd is defined in Part 23 23.335 (see above where design airspeeds are Equivalent Airspeeds)

 (b)Design dive speed VD. For VD, the following apply:

(1)VD/MD may not be less than 1.25 VC/MC; and

(2) With VC min, the required minimum design cruising speed, VD (in knots) may not be less than—

(i) 1.40 Vc min (for normal and commuter category airplanes);

(ii) 1.50 VC min (for utility category airplanes); and

(iii) 1.55 VC min (for acrobatic category airplanes).

[mooniac15u]

And it is adjusted by altitude because???

(Hint: the red line IAS that yields the Vne TAS decreases with altitude!)

 

For a given IAS the corresponding TAS changes with altitude.  That has absolutely nothing to do with Vne in a certificated aircraft like ours.  Vne is quite simply and quite clearly an IAS per the certification process.

[PTK]

As I said, this is to present it to the pilot quick and easy with safety margins built in.

Your point is...

It has everything to do with Vne being a TAS! Everything!

[Marauder]

I got an easy answer to this challenging problem you guys are trying to solve; don't go too fast!

Peter you seem to want to prove your theory, I'll loan you a Garmin VIRB that you can point at your tail & two GoPros that you can point one at your ASI and the other at your face. Go up to 15,000, point the nose down and see what speed your tail comes off.

We'll report the results and post the videos for you...

Sent from my iPad using Tapatalk

[Bob_Belville]

I'm waiting for Mike, Don, or some other working CFI to weight in on what they expect students to know about Vne. I sometimes descend at the red line in my 50 year old M20E which is only 164k (189mph). I've always behaved as if that could be done using IAS but I believe putting the needle there is a bad idea, even at 5-10k feet.

[DS1980]

I like this discussion. Lots of explanation and patience on both sides.....input eyes rolling emoticon here.

 

Wondering what happens when folks realize Vne is TAS.

 

Proud of Pete for sticking to his guns.

[Andy95W]

I'm waiting for Mike, Don, or some other working CFI to weight in on what they expect students to know about Vne.

What I expect a student to know about Vne:

"See that red line? Don't let the airspeed needle go above it."

[mooniac15u]

There seems to be a lot of confusion here between the physical limitations of our aircraft vs the legal limitations of our aircraft. Sometimes these are the same (Vs) sometimes they are not (Vne).

Vne is a legal limitation. It is designed to protect you from encountering the physical limitations of your airframe.

The physical limitations are absolutely related to TAS. The legal limitations are IAS. Only the FAA gets to define legal limitations and they are very clear in defining Vne as an IAS.

Think of Vne like max gross weight. Is max gross weight a physical limitation of your airframe? No, it is a legal limit below which your aircraft operates in a safe and predictable way. Vne is a legal limitation below which your plane will operate in a safe and predictable way.

[Bob_Belville]

What I expect a student to know about Vne:

"See that red line? Don't let the airspeed needle go above it."

Interesting Andy. do you know if the PPL written has any questions like Vne is expressed in: a) IAS, CAS, c) TAS, d) other?

[Shadrach]

I like this discussion. Lots of explanation and patience on both sides.....input eyes rolling emoticon here.

Wondering what happens when folks realize Vne is TAS.

Proud of Pete for sticking to his guns.

Show us please! Everyone agrees the true airspeed has the largest impact on flutter. However we're not talking about flutter, we're talking about Vne which has a whole host of design limits incorporated into it. So show me something regulatory that tells us Vne is a TAS number. If you can do that I will happily agree with you. This post has included screenshots of the TCDS, the relevant FAR's and then a bunch of people on the internet contradicting The FAR with no documentation to back it up.

I'm happy to agree with you and Pete, if you give us something other than your opinion. Show me something regulatory!

[Cyril Gibb]

VNE is based on IAS and is established to limit overstressing due to load factor.

Flutter speed is based on TAS.

Two separate limits. First one is in the POH and TCDS. The second isn't.

The next question is the TAS that can induce flutter in various flavours of Mooneys.

[Andy95W]

Interesting Andy. do you know if the PPL written has any questions like Vne is expressed in: a) IAS, CAS, c) TAS, d) other?

I'm stayin' out of it.

[Bob_Belville]

There seems to be a lot of confusion here between the physical limitations of our aircraft vs the legal limitations of our aircraft. Sometimes these are the same (Vs) sometimes they are not (Vne).

Vne is a legal limitation. It is designed to protect you from encountering the physical limitations of your airframe.

The physical limitations are absolutely related to TAS. The legal limitations are IAS. Only the FAA gets to define legal limitations and they are very clear in defining Vne as an IAS.

Think of Vne like max gross weight. Is max gross weight a physical limitation of your airframe? No, it is a legal limit below which your aircraft operates in a safe and predictable way. Vne is a legal limitation below which your plane will operate in a safe and predictable way.

Okay. Does that imply there is an adequate safety factor in the FAAs selection of Vne to allow me to take my M20E to its service ceiling of about FL190 and then descend @ the red line speed which will at that altitude will be a TAS far in excess of the 164k Vne? 

[mooniac15u]

Okay. Does that imply there is an adequate safety factor in the FAAs selection of Vne to allow me to take my M20E to its service ceiling of about FL190 and then descend @ the red line speed which will at that altitude will be a TAS far in excess of the 164k Vne? 

 

That is the regulatory implication.

 

I do not personally think that would be a good idea.  If you hit a single gust or bit of turbulence you will likely exceed Vne.  Then you will be a test pilot and you will not know for sure that you haven't damaged your aircraft by exceeding load limits.

[Bob_Belville]

That is the regulatory implication.

 

I do not personally think that would be a good idea.  If you hit a single gust or bit of turbulence you will likely exceed Vne.  Then you will be a test pilot and you will not know for sure that you haven't damaged your aircraft by exceeding load limits.

Okay, "regulatory implication". And the FAA would have based that on what? Did Bill Wheat do something like what I described? 

 

I do not mean to insult when I ask for the basis of your assertion. I'm sure it is documented somewhere pretty wonky.

[Super Dave]

PTK and DS 1980,

You are absolutely correct that flutter is a function of TAS, but flutter speed and Vne are not interchangeable terms.

As others have pointed out Vne is clearly defined as an IAS.

In a certificated airplane operated within it's envelope, Vne will protect you from flutter (and other bogeymen). There is no need to calculate TAS or density altitude, just keep the white needle below the red radial and all the pieces should stay attached to the airplane.

[Shadrach]

Okay. Does that imply there is an adequate safety factor in the FAAs selection of Vne to allow me to take my M20E to its service ceiling of about FL190 and then descend @ the red line speed which will at that altitude will be a TAS far in excess of the 164k Vne? 

 

. 

I've not been to 19,000 feet in my F.  However I have been to DA's above 18,000 (about 14,500MSL on a hot day).  Vne for my bird is 174KIAS.  I descended at 170KIAS down to about 2500MSL. No Drama, no bumps, no problem.  I'm not suggesting you do it. Just letting you know that it's a non-event if you ever find yourself needing to go down ASAP.

[Shadrach]

Okay, "regulatory implication". And the FAA would have based that on what? Did Bill Wheat do something like what I described? 

 

I do not mean to insult when I ask for the basis of your assertion. I'm sure it is documented somewhere pretty wonky.

 

 

I would bet dollars to donuts that Bill Wheat has ridden the M20 airframe down from altitude at speeds that would make your Vne look slow.