OK. The answer is in from: The landing gear has nothing to do with limiting take off speed but the brakes are a critical part of the runway length requirement. So,
the answer is, "False".

Following spinnaker's initial inquiry, the questions I'd be asking instead are:

1. What are the landing gear's wheels maximum rpm's?
2. At what speed does the "ground effect" of a plane become uncontrollable?

 

Looking at 2) first, when sufficient airspeed is attained it will be hard if not impossible to keep the plane on the ground - it is designed to fly after all. The particular speed depends on the airplane. An Aero-Commander has a negative angle of incidence and wants a definite rotation to take off. A typical light plane like a Cessna or Piper has a positive angle of incidence so it will fly off at a surprisingly low airspeed with no control inputs at all. 1)AFIK, flight happens way before you exceed any wheel speed limitations. Trying to keep the plane on the ground at flight speeds is likely to end badly. Unless you are flying an SR-71, wheel speed is probably not an issue.

 

Following spinnaker's initial inquiry, the questions I'd be asking instead are:
1)What are the landing gear's wheels maximum rpm's?

1. At what speed does the "ground effect" of a plane become uncontrollable?

1) I think you mean, "tires".
2) I think you mean the effect of the proximity of the plane to the ground surface, like a race car, and John answered a completely different question, as if ground effect has nothing to do with airplane because their wings are not one to two inches above the asphalt.

 

I lived and worked in San Diego in the 70's. We would ride our bikes to Mt. Palomar or up and down 101 on the weekends. I left in 90 and have never regretted the move north.

Sweet bike, you and @#12 both had good rides.

kv

 

Sweet bike, you and @#12 both had good rides.

kv

And they are similar in the color theme.
Different engine, transmission, seat, but the colors are the same.

 

John answered a completely different question, as if ground effect has nothing to do with airplane because their wings are not one to two inches above the asphalt.

Fair point, I lumped ground effect with normal lift together. Ground effect is still a factor in takeoffs, though.
https://en.wikipedia.org/wiki/Ground_effect_(aerodynamics)

Anyway, back to weather..

 

"When an aircraft flies at a ground level approximately at or below the length of the aircraft's wingspan"
Got it. (Got schooled again, today.)

And a great yuge mass of rain is pulling clouds up from the south, running right over me. Looks like rain all night.

 

"When an aircraft flies at a ground level approximately at or below the length of the aircraft's wingspan"
Got it. (Got schooled again, today.)

And a great yuge mass of rain is pulling clouds up from the south, running right over me. Looks like rain all night.

Utah has one, seems to be stopping though. Wing span never even came to thought.

kv

Edit: Maybe not from the south.

 

It's been awfully hot and humid today, but at least we're enjoying a beautiful sunset... as seen from my backyard

​

 

Smog and over crowding.

Speak of the devil:

http://www.cbsnews.com/news/worst-air-quality-california/​

 

That's what I have doubts about.
According to the Guiness Book of World Records, the lowest sea-level
pressure ever recorded was 25.69 inches in the storm Typhoon Tip.
http://www.faqs.org/qa/qa-20260.html
Let's go do Denver at 5000 ft.
24.9" Hg.
If Denver had a world record hurricane, the atmospheric pressure would be 20.59 inches of mercury.
That's about 2/3 of normal air density.
Gee, I wish an airplane guy would show up.

Thanks for the tag.

Air pressure doesn't equate to air density.

There are a lot of factors that determine takeoff distances, but density altitude is a huge one (weight is the real big one, though).

"Pressure altitude" is the altitude in the "standard atmosphere" that would have the same pressure as the actual pressure. Density altitude is pressure altitude adjusted for temperature and is the altitude at which the air density in a standard atmosphere would be the same as the actual density. Humidity also plays a role, but it is less pronounced.

The engine and airfoil performance is primarily dictated by the air density (turbocharged engines are a different critter, so I'm only talking about normally-aspirated internal combustion engines).

The airspeed that most performance curves use is the "indicated airspeed", or IAS, which is affected by air density since part of the sensing system uses impact forces and the less dense the air is the less the impact force. The instrument is specifically designed this way so that it corresponds well to aircraft performance over the bulk of the operating envelope. The "true airspeed", or TAS, is the real speed that the aircraft is traveling through the air mass.

I can't speak to jet aircraft, but for small, general aviation aircraft the rule of thumb is that you have to increase the takeoff distance by 10% for every 25°F above the standard temperature.

For a T-41D, the aircraft that most of my time is in and can largely be thought of as a Cessna 172 with an attitude, the calm-air ground roll for takeoff (with 10° flaps) is 740' at sea level (59°F) with an IAS at 50' altitude of 71 mph. It's 1065' at 5000' (41°F) with an IAS at 50' of 61 mph. That is for operation at the max gross takeoff weight of 2500 lb. At a weight of 1900 lb the distances are roughly half this at 380' and 540', respectively (same airspeeds).

Sky Harbor sits at a runway elevation of 1135'. The standard temperature decreases at 2°C/1000' (gotta love the mixed metric/imperial units), or about 3.5°F/1000', so the standard temperature at Sky Harbor is right about 55°F. If Sky Harbor was at normal pressure, then at a temperature of 120°F they would have a density altitude of approximately 5000'. That's not outrageous, considering that the number of times that I've taken off from a runway that was less than that can almost be counted on my fingers. The takeoff roll would be about 25% longer.

Landing distances are not as thoroughly documented as takeoff distances. The only entries in the manual for the T-41 is for 2500 lb at an IAS of 75 mph. At sea level it is 610' and at 5000' is 685'. These are for standard temperature and there are no adjustments given. The big thing to take into account is the difference between TAS and IAS.

I just checked Sky Harbor ATIS and their present temperature is 118°F and their altimeter setting is 29.63" Hg. Their reported density altitude is 5195' (so my 5000' estimate was pretty darn close). Using an online calculator (since I don't know where my trusty E6B is right now) their pressure altitude is 1405' and an IAS of 75 mph would be a TAS of 81 mph. So your landing roll would be increased by the distance it takes to slow from 81 mph to 75 mph, roughly. But that is also the TAS at 5000' at 41°F, so you can expect a rollout of about 685'.

But takeoff and landing speeds are only part of the equation. Once you are off the ground your plane thinks and performs like it's at a higher altitude. It climbs more slowly. When I was flying out of the Academy (6515' MSL) if the density altitude exceeded 9000' then the older C-172's were not allowed to operate. The newer 172's could still operate until we hit 9500' and the T-41's were allowed to go until we hit 10,500'. I'm not positive, but I believe these were based on the point when your max rate of climb at max gross weight fell below about 300 ft/min.

Now, having said all of that, I'm a bit at a loss as to why Sky Harbor would cease operations with a D.A. of only 5000 ft. I haven't read the article -- is it the airport that closed operations or the individual airlines canceling flights? To compensate for the heat, large aircraft have to reduce their loads (less passengers and less fuel) so it might be an economic decision as well as a safety one. I would imagine that, like the Academy, they set operating limits on a per-aircraft-type basis taking a lot of factors into account. One thing to keep in mind is that an airliner climbs to it's cruising altitude of about 35,000' in a short period of time where the temperatures are about -60°F. Having your airframe go through a 200°F differential in the span of ten minutes or less probably isn't a good thing for the life expectancy of a plane you plan on operating for several decades.

 

Speak of the devil:

Old story, but I'll tell it again.
In 1974 I went to Orange Hill restaurant and watched the fireworks at Disneyland over a Tequila Sunrise.
In 1985, I tried the same thing and the only color I could see was red.
Today is 32 years later.

Every person that used to live in California complains about how much better it used to be.
I loved it in the 1970's while people from the 1960's were telling me how bad it became.
I was there in the '70's and I can tell you it looks awful from here.

 

In 1974 I went to Orange Hill restaurant and watched the fireworks at Disneyland over a Tequila Sunrise.

I thought you didn't drink...

 

@WBahn

Now, having said all of that, I'm a bit at a loss as to why Sky Harbor would cease operations with a D.A. of only 5000 ft.

The Bombardier CRJ is limited by the POH to ISA + 35C ambient. Other planes didn't have a problem.

 

1) I think you mean, "tires".
2) I think you mean the effect of the proximity of the plane to the ground surface, like a race car, and John answered a completely different question, as if ground effect has nothing to do with airplane because their wings are not one to two inches above the asphalt.

Ground effect is quite pronounced for an aircraft. The rule of thumb is that it is a big factor when the wings are less than half the wingspan above the ground.

I witnessed a Cessna 182 crash at the Pueblo, CO airport on a hot summer day. The plane took off and immediately sank down to about 15' above the ground in a nose up attitude. I was running the flight line that day and remarked to the cadets I was supervising as he went past that he was in trouble. Then I started screaming at him (as if he could hear me -- yeah, right) to cut the power and set it down. He was trapped in ground effect -- that gave him enough lift to stay off the ground but as soon as he tried to climb out of it he lost the additional lift from ground effect and mushed back down into it. But he kept trying to take off and then made the ultimate mistake -- when he got past the end of the runway and realized it wasn't going to happen, he tried to turn back to the airport, thus losing a significant amount of the vertical component of lift. I screamed, "NO!!! DON'T TURN, DAMN IT!!" at the top of my lungs. Quite predictably, he put the left wing tip into the ground and cartwheeled.

When I was giving my statement to the sheriff (for his report to the NTSB) I mentioned that I suspected he hadn't leaned his mixture before takeoff. Sure enough, when the report came out, the cause was pilot error on several fronts. Failing to lean the mixture prior to takeoff (below 3500' you don't lean and this guy was from back east and this was his first time taking off from an airport higher than that), failure to recognize the inability to climb when there was still time and runway to abort, and loss of control resulting from attempting to turn when what he should have done was do the best off-field landing he could straight ahead making only minimal turns to avoid obstacles (of which there really weren't any).

 

@WBahn The Bombardier CRJ is limited by the POH to ISA + 35C ambient. Other planes didn't have a problem.

So for Sky Harbor that would limit them to 118°F.

I wonder what the rationale for the limitation is.

 

Air pressure doesn't equate to air density.

Just showing off my ignorance.

impact forces

Strong awareness of velocity pressure vs static pressure because A/C fans.

I thought you didn't drink...

I didn't drink alcohol or, "consort" with women since about 1995. I didn't smoke pot since about 1985. I didn't ride a motorcycle or drink Yerba Matte' since June 25, 1976. I didn't live in Indianapolis since January 20, 1970.

People change. I wasn't born 66 years old.

 

So for Sky Harbor that would limit them to 118°F.

I wonder what the rationale for the limitation is.

Probably a combination of things. For a 121 operator there are lots of performance requirements that 91 or 135 guys don't worry about. I speculated on some of that here along with the snippit from the POH.
https://forum.allaboutcircuits.com/threads/air-density-and-runway-length.137202/#post-1147884

 

Probably a combination of things. For a 121 operator there are lots of performance requirements that 91 or 135 guys don't worry about. I speculated on some of that here along with the snippit from the POH.
https://forum.allaboutcircuits.com/threads/air-density-and-runway-length.137202/#post-1147884

So it looks like it might be a limitation to the calculated limits consistent with "max demonstrated" performance.

The Air Force likes to hold Aeroclub members to those numbers, which is a pain because the maximum demonstrated crosswind component is usually pretty low and with so many airports having only a single runway it can really clamp you down. I've landed significantly above those limits -- one night I landed with the rudder at the stops! I won't take off above the book limits -- there's no need to push it when you have the option of just waiting it out. But when you're up in the air at the end of a long flight and only a few airports with lights in range of your reserves (and all likely having similar weather) I tend to become a lot more ... daring... and willing to exceed the limits at the one airport with a 9000 foot long, 100 foot wide runway that has VASI lights. Thank heaven for pilot-controlled lighting!

 

it's a great weather outside, warm and sunny