VNE and Flight Limitations at Alititude

[Pur_SSyn]

Hello, all! I'm new here and would like to learn about physics of flight to help clear up a
debate between friends.



Our discussion revolves mostly around flight limitations at certain altitudes, and the physical
limitations of aircraft.
We're using either of the following airplanes in our analysis: DC10, 707, 757, 767
My questions are:
1. What is the maximum landing speed of either plane in Knots, or MPH?

2. What is the maximum approach speed of either plane in Knots, or MPH?

3. VNE - Velocity do not exceed. What is a typical VNE at 1000 feet altitude, and
how much (if any) can you exceend VNE without stressing the structure of the aircraft?

4. Effects of atmospheric pressure and altitude on speed. Is an airplane able to fly
as fast at sea level as it can at 35,000 feet? If not, how much slower can we expect
to fly at sea level?

I wont give my opinions, however I will say that I believe:
1. Max landing speed for either of those planes is approximately 150-200 knots

2. Max approach speed for either of those planes is apporximately 150-200 knots

3. VNE may be exceeded , however not recommended. VNE could never be doubled safely
at any altitude.

4. No, an aircraft cannot fly as fast as sea level because of aero drag due to atmospheric
pressure. For every 1000 ft. of decent, subtract about 5 MPH?

Thanks for your time!

[Check Airman]

1. What is the maximum landing speed of either plane in Knots, or MPH?

2. What is the maximum approach speed of either plane in Knots, or MPH?

Both will depend primarily on weight, and then airplane configuration. Each type will have a maximum speed for landing flaps, and a maximum tire speed.

What is a typical VNE at 1000 feet altitude,

Around 340kt for the types you have there. It varies with altitude.

how much (if any) can you exceend VNE without stressing the structure of the aircraft?

You'd have to ask the manufacturer, or the pilots who did initial certification testing.

Is an airplane able to fly as fast at sea level as it can at 35,000 feet? If not, how much slower can we expect to fly at sea level?

The indicated speed and mach speed limits will change, but jets will fly faster (TAS) at higher altitudes.

[nugpot]

Pur_SSyn, I will keep my answers slightly less technical, so they are more rules of thumb than the absolute truth.

1. What is the maximum landing speed of either plane in Knots, or MPH?

Most of the aircraft you named will have normal landing speeds of between 130 to 150 kts. In abnormal conditions (flap problems or other abnormal configuration), this speed will increase, but as mentioned will be below the tire limiting speed of usually around 180kts.

2. What is the maximum approach speed of either plane in Knots, or MPH?
Most aircraft will attain very close to their touchdown speed quite early on final approach, because most airlines have a "slot" between 500 - 1500 feet above ground where you have to be at your approach speed (called Vref). So final approach speeds are also between 130 - 150 kts.

What is a typical VNE at 1000 feet altitude?
Most modern airliners have a lower level Vne of between 330 and 350kts. It will not be exceeded by line crews during normal operations and we don't consider any safe margin beyond Vne.

Is an airplane able to fly as fast at sea level as it can at 35,000 feet? If not, how much slower can we expect to fly at sea level?
This is slightly more complex. Aircraft are limited at the higher levels by a Mach limit (called Mmo). This is due to compressibility effects at high Mach numbers. It is usually in the region of M.78 to M.88.

It would be easier if I answer your question by working in TAS (True Airspeed). At the lower levels TAS is close to IAS (Indicated Airspeed). Vne is an IAS limit, so max TAS at lower levels would be between 330 - 350 kts.

At altitude, TAS would be around 430 - 480 kts, so in still air, the aircraft would be over 100kts faster at altitude.

Somewhat off the subject. At altitude you can get winds of over 150kts, so it is conceivable that an aircraft at altitude with a strong tailwind could achieve over 600kts over the ground.

Like I said, this is a slightly simplified version of the true physics involved, but good enough for your argument.

[Pur_SSyn]

Thank you both for the information. This is enough to help out and
confirm my thoughts.

It's nice to know I have some pro's in my corner with real world facts.

[john_tullamarine]

.. but keep in mind that most jets are designed to Vmo/Mmo, rather than Vne.

For those aircraft which use Vne, it is a HARD limit. There is some fat in the design and test program but, for the line pilot, one doesn't exceed Vne.

Vmo, on the other hand is able to be exceeded for specified reasons and it is not at all uncommon for Vmo to be exceeded by a small margin on descent until the pilot has time to reduce the speed a little to get back under the clacker ...

[Pur_SSyn]

Thank you for the additional info John.

In flight terms, would Mmo (max. mach) and Vmo (max. velocity) be
rated higher than Vne?

Would you happen to have approximate values for Vne, Vmo and Mmo for
a two seater, single engine plane such as a Katana DA-20?



Sorry for the very basic questions; I'm just learning about aero physics
and don't really know where to go.

I'm also looking to debate a few points with my friends who claim
they were in airplanes that approached runways at twice Vne
(Katana DA 20),
or flew over landing strips at 220 knots and 1000 feet altitude
(Airbus 330 flying into Denver airport).

It just seems very odd, and against regulation to me.

[john_tullamarine]

... would Mmo (max. mach) and Vmo (max. velocity) be
rated higher than Vne?

One or the other. The basic rules for US certification for you to review are at

(a) FAR 25.1505

(b) FAR 23.1505

For lighties (or any aircraft for that matter) the basic certification data is in the Type Certificate Data Sheets (TCDS) which, for the US case, can be found at the FAA's TCDS site.

... they were in airplanes that approached runways at twice Vne

I have no specific knowledge of the Katana .. but, I don't think so ...

... flew over landing strips at 220 knots and 1000 feet altitude
(Airbus 330 flying into Denver airport).

not the norm, I would suggest, but certainly not outside the routine capability of the typical airliner and crew ...

[Pur_SSyn]

Thank you again John.

Just for sake of record, would all of you mind posting a short summary of
your pilot profiles?

John, I see that you are an engineer and pilot. Would you be able to
elaborate on your flight experience? This would be used to qualify the
data used in my debate.

Finally, would either of you mind:

a. if my friends joined this site to continue to debate among the professional pilot community?

b. giving e-mail (via Private Message) to join our e-mail thread
off-line

Thanks for your help in any case.

[john_tullamarine]

Most of us put that which we wish to be public in the profile albeit that bits and pieces often get added in various posts.


Regarding your friends, so long as the discussion retains a value for the flying community that would be fine.

[411A]

.. but keep in mind that most jets are designed to Vmo/Mmo, rather than Vne.

This is quite true, however a few types that some might think would not qualify for a hard limit Mne, have one.
Example.
DC-7 and Lockheed 1649 Constellation.
Even the B377 type certificate was amended later on to reflect changes to the original flight test data.
Looking at a Stratocruiser one might not imagine it could be flown fast, but looks could be deceiving.
It had very large engines and pointed downhill, the acceleration was quite rapid.

[RonaldWieck]

As I lack a background in avionics, I consider myself fortunate to have found such a valuable resource as this forum. The knowledgeable people here should be aware, however, that a bizarre subset of the 9/11 conspiracy cult believes that no planes were involved in the events of that terrible day. To promote this mad thesis, these "no-planers" try to twist the words of pilots and aeronautical engineers to "prove" that UA 175 could not have been flying at roughly 550 mph when it crashed into the South Tower. When someone appears to inquire innocently about the speed limit of a Boeing 767 at sea level, please understand that a "truther" is playing a perverse game.

[Pur_SSyn]

No planes on Sept.11th? That's some funny stuff! Video proves planes
crashed into the towers, but don't think I'm on your side of debate on the
subject.

I dare you all to read this entire post:

Flying at well over VNE, and hitting a 200 foot wide wall at 500+ knots,
three times, by three different rookie "pilots" is quite a funny story.
You figure that most rookie pilots can't line up with a runway at 1/5th of
the speed, using IFR methods (ILS approach for instance), but you're willing
to accept that an aircraft can dive out of the sky with little to no correction
while their wings, rudder, elevator, and ailerons are freaking out at 530 Knots and line up with their 'runway'? Can you imagine the pressure on the
stick, and how difficult it would be to control?

One aircraft flying toward P-56 (no fly air space) without a blink from the
military? Hmmm...

Let's not debate the "probable"...one only needs to look at WTC 7 falling
exactly like a controlled demolition, with accelerating motion to telescope
down in 6.5 seconds (47 story, steel framed building).

So yes, I may have played a bit of a game to seek approval from fellow
aviators, but that's what it takes when some people want to scold you
for asking questions.

I wont be surprised if this post gets removed, or my account gets locked
for this response, however for the person(s) that acts upon this:

Do yourself and your fellow friends a favour and actually research WTC7
and some of the facts surrounding the event. Did you know war games
happened on 9/11? Admitted by the Pentagon. Four simulated hi-jacks.
Coincidence?

Did you know 1664+ Architects, scientists and structural engineers
put their name on the line to explain the impossibility of WTC7 collapse,
as well as finding traces of explosive residue in the dust?

Call me crazy, or a truther if you must. I'd rather be called either of those,
than be ignorant of the facts, or uneducated to understand the physics
surrounding the WTC 7 collapse garbage.

Be well folks. Don't be scared to ask questions, or look deeper into the
story via independent sources. It doesn't make you unpatriotic, it makes
you a normal human.

[galaxy flyer]

Four plus years on, and this reopens with silliness?

I know one of the AA's captains brother, who ran for Congress, btw. He hasn't seen his brother since 9/10. Where might he be , if there were no planes?

P-56? It has been, and continues to be, penetrated by all sorts of KDCA departures with reasonable regularity. As in, about 4-5 times a year. It used to be more often but GA traffic has been basically eliminated from the airport. In the old days, there was no airborne military component in the DC area. I won't discuss the pre-9/11 alert status. Since 9/11, the USCG and USAF have a presence and are set to intercept intruders in the DCA SFRA. In all cases, past and present, the FAA had a very strong reaction to P-56 intruders. The penalties were high and not avoiding them.

You want to peddle conspiracy theories, I'd suggest knowing some facts.

GF

[stilton]

Er Pur,


You are Bonkers.

[aerobat77]

i think everyone who believes that 9/11 was a big goverment inscination should ask himself : for what?

for having arguments in attacking afghanistan ?

i think they should be able to find a far cheaper way to find such arguments than crushing their major skyscrapers in the heart of new york, kill thousands of their own citizens ,destabilize their own financial market and harm their own civial aviation market.

i do not see any benefit for the goverment in inscinating such a thing like 9/11 - and i think thats the best provement it was true .

cheers

[Pur_SSyn]

I may be bonkers, but I do believe planes were used that day.

If you can't explain how building 7 (WTC #7) fell in 6.5 seconds like a controlled
demolition without the aid of explosives, then you may be crazy as well.

Further to that fact, the chips within the dust have the same chemical
signature as thermitic material post-ignition, and outperform a labratory high grade explosive producing more heat within a shorter period of time (IE: more energy released in an explosive fashion).

Please don't call me bonkers without researching those points and explaining how it's possible.

If you want some bonus material, let me know how 757 wings would handle
five steel street lamp poles getting thrown at them at 460+ knots and level off at 20 feet above the ground and still be able to hit a target 300 feet away.

Anyway, thanks for the somewhat civil response.

[galaxy flyer]

If you want some bonus material, let me know how 757 wings would handle five steel street lamp poles getting thrown at them at 460+ knots and level off at 20 feet above the ground and still be able to hit a target 300 feet away.

Clearly, you know little or nothing, make that nothing, about the physics of an aircraft impact.

WTC 7's fall has been explained conclusively by any number of engineers. A building collapsing falls at very nearly the acceleration of gravity. WTC 7 burned, unfought, for hours as the initial rescue efforts were at the towers. It collapsed just like they did, just took longer.

Since it has been mentioned, bonkers is the only civil answer to you conspiracy theorists on 9/11. How about where was Obama born, who killed Kennedy and did FDR know about Pearl Harbor.

gf

[Pur_SSyn]

Well, 1664+ engineers say you're wrong, and your answer doesn't explain
the chips that release more energy in a shorter period of time than a known
explosive comparison sample.

Clearly you haven't researched any of this and believe a rookie pilot can
dive out of the sky at 500+ knots (ground speed) and line up with a 200 foot
wall (unassisted).



If yuo're happy with your research and think a building can fall straight down
in 6.5 seconds from 47 stories having SMALL OFFICE FIRES and ASYMETRICAL
damage, then all the power to you!

I didn't know a few small offices fires on select floors could take down a
building and produce explosive residue in the debris pile.

You might want to weigh/review all the facts and produce a response that satifies
all before you reply.

While you're at it, please post a link to the "fires" in WTC7 prior to collapse.
You'll soon see, that the insignifiance/lack of fire refutes what you believe.

[Wizofoz]

Well, 1664+ engineers say you're wrong,

Debunking 911 Conspiracy Theories and controlled demolition - Structural and Civil Engineers against Controlled Demolition

You're a whacko.

[chubbychopper]

Pur. I think you are in need of a check up from the neck up.