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FAR 23 limiting stall speeds to 61 knots
Originally 70mph prior to metrication. From a discussion with an ancient engineer chap who was in the precedent organisation in the early days as a boy, 70mph was a figure plucked out of the air by the senior folk as being a reasonable starting point to put into the rule book .. and then it just stayed and was never altered. |
J_T
Always wondered where 61 knots came from--rather odd sounding. But metrication? Perhaps, metrification or nauticalification? GF |
It's not really metrication, is it ? I ought to be a tad more precise at times .. have to blame the advancing decrepitude, I guess ...
(a) current rule (b) old FAR 23 rule which changed to 61 kt at A/L 23-7 Sep69 (c) CAR 3 goes back to 1949 (refer 3.83). I don't have any Net references to earlier US regs but, no doubt, someone else in the sandpit will be able to cite a link to the real olden days .. 1949 - I was too young to have much of an interest in aeroplanes .. Here endeth the useless bit of information for the day ... |
Some pre-incarnation of CAR3 goes back to 1930s. Even racing aircraft of that era were designed to a Vso of 70 mph. :8
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No wonder I can't fly an ILS; too much metriculation manoeuvreing conversion calculations !
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Boy, am I sorry I brought this up!
GF |
John Farley,
Thanks for responding to my request. You clearly are familiar with a lot of aspects of aircraft design and performance but I feel have got some of the basic building blocks a bit jumbled up in your head. I will PM you with some of the basics of lift and drag which I think might help you straighten out some of your concepts. The stall speed which will be 1.414 times what it was before (this will up your takeoff and landing speeds and distances) The aircraft will have much more inertia (this will make the aircraft appear ‘sluggish’ in response to you trying to change its flight path The manoeuvre boundary is a measure of how much g you can momentarily pull at a particular speed (this will reduce as wing loading goes up) The thrust boundary is a measure of how much g you can sustain without loss of airspeed and is primarily affected by the thrust available. It will suffer as you put up the wing loading but likely less than the manoeuvre boundary. cwatters, Reynolds number. Big fast wings are more efficient than small slow ones. Willit Run, No wonder I can't fly an ILS; too much metriculation manoeuvreing conversion calculations ! |
The maximum instantaneous g-load you could pull without getting an accelerated stall? When briefing for tests to get this data the most important thing is the characteristics that the team choose to define the stall. (wing drop, buffet level, sideslip behaviour and so on) |
John Farley,
No. You will have to reach the stall otherwise how do you know you have reached the max g? |
The boundaries can only be fully established by flight test.
Tunnels are just one of the estimation tools available - but estimates are just that estimates. . |
John Farley,
The boundaries can only be fully established by flight test. |
galaxy flyer,
Transports don't engage in turning fights for survival or "scissor" with another plane to get landing priority. |
Knots (kts) = nautical miles per hour (nmph).
1 nautical mile = 6,000 feet. 1 statute (land) mile = 5,280 feet. MPH = statute miles per hour 1 mile = .88 nmile None of this has anything to do with the metric system. KPH = kilometers per hour 1 kilometer ≈ 3,281 feet ≈ .62 mile ≈ .547 nmile |
A nautical mile is 6076 feet not 6000
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None of this has anything to do with the metric system |
Although it's conventional to think about the "metric system" in terms of metres (= 1/40,000,000 of the circumference of the Earth at the equator), today the metre is better defined, and it's all called SI (systeme internationale d'unites). I tend to think of ANY system as "a metric system".
And so the nautical mile is 1 minute of longitude at the equator, so = 1/(360x60) of the circumference of the Earth at the equator. |
And so the nautical mile is 1 minute of longitude at the equator, so = 1/(360x60) of the circumference of the Earth at the equator. The nautical mile was historically defined as a minute of arc along a meridian of the Earth, making a meridian exactly 180×60 = 10,800 historical nautical miles. It can therefore be used for approximate measures on a meridian as change of latitude on a nautical chart. The originally intended definition of the metre as 10−7 of a half-meridian arc makes the mean historical nautical mile exactly (2×107)/10,800 = 1,851.851851… historical metres. Based on the current IUGG meridian of 20,003,931.4585 (standard) metres the mean historical nautical mile is 1,852.216 m. The historical definition differs from the length-based standard in that a minute of arc, and hence a nautical mile, is not a constant length at the surface of the Earth but gradually lengthens with increasing distance from the equator, as a corollary of the Earth's oblateness, hence the need for "mean" in the last sentence of the previous paragraph. This length equals about 1,861 metres at the poles and 1,843 metres at the Equator. Other nations had different definitions of the nautical mile. This variety in combination with the complexity of angular measure described above along with the intrinsic uncertainty of geodetically derived units mitigated against the extant definitions in favor of a simple unit of pure length. International agreement was achieved in 1929 when the International Extraordinary Hydrographic Conference held in Monaco adopted a definition of one international nautical mile as being equal to 1,852 metres exactly, in excellent agreement (for an integer) with both the above-mentioned values of 1,851.851 historical metres and 1,852.216 standard metres. Use of angle-based length was first suggested by E. Gunter (of Gunter's chain fame), reference: W. Waters, The Art of Navigation in England in Elizabethan and Stuart Times, ( London, 1958). During the 18th century, the relation of a mile of 6000 (geometric) feet, or a minute of arc on the earth surface had been advanced as a universal measure for land and sea. The metric Kilometre was selected to represent a centisimal minute of arc, on the same basis, with the circle divided into 400 degrees of 100 minutes. |
Thanks for the upgrade; however MY navigation was never that precise! :O
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When getting to the seventh significant figure, do we need to consider the effect of global warming on sea level and hence on the earth's circumference? Or the fact that aeronautical miles are longer because the earth's circumference is greater when at altitude?
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mike-wsm,
Very good observation about the distances being greater at altitude. If you drew a line 30,000 feet up in the air at your takeoff and landing points you technically cover a little bit more distance than if you were at sea-level the whole time. |
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