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It seems to be agreed (at an international level) that these values are standard and should be respectively 50 ft and 3 degrees. Are all airports following these rules, and are they applied to all type of aircraft?

Why would departure operations not have the same kind of constraints?

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  • $\begingroup$ The short answer is "no", especially for TCH. (Long answer will come later today if nobody else gets it :) $\endgroup$
    – UnrecognizedFallingObject
    Mar 7, 2017 at 12:33
  • $\begingroup$ LCY (London City) has an approach that is 5.5 degrees, and it used to be 7.5 degrees at one point in the past. I also know some short-field approaches if you are 50' over the threshold when crossing it, you are going to end up in the bushes at the end of the runway. $\endgroup$
    – Ron Beyer
    Mar 7, 2017 at 12:59
  • $\begingroup$ @UnrecognizedFallingObject, I will accept Gerry's answer, but your input is more than welcome! :) $\endgroup$
    – harveyAJ
    Mar 8, 2017 at 9:37
  • $\begingroup$ @harveyAJ -- I'd just have restated what Gerry said $\endgroup$
    – UnrecognizedFallingObject
    Mar 8, 2017 at 12:47

2 Answers 2

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In the US, the requirements are specified in FAA Order 8260.3, United States Standard for Terminal Instrument Procedures (TERPS).

Section 2-3 states:

2-3. General PA Requirements. See Order 8260.19 for requirements related to GPA/TCH coincidence.
a. GPA. Utilize a standard 3-degree GPA where possible. GPAs greater than 3 degrees but not more than the maximum (table 2-1) are authorized without approval when needed to provide obstacle clearance or to meet simultaneous parallel approach standards. Other cases or GPAs less than 3 degrees require Flight Standards or military authority approval (USAF not applicable).
enter image description here

b. TCH. The published TCH (nearest whole foot) should accommodate the largest aircraft height group normally expected to use the runway and must not be less than the minimum or exceed the maximum TCH. Note: 60 feet is the maximum TCH regardless of height group.
(1) CAT I. The TCH is based on achieving an acceptable wheel crossing height (WCH). The WCH is the difference between the TCH and the approximate glidepath antenna-to-wheel height (see table 2-2).
(a) The optimum TCH provides a 30-foot WCH. It must provide a WCH no less than 20 feet or greater than 50 feet.
(b) Displaced Threshold Considerations. The TCH over a displaced threshold can result in a WCH of not less than 10 feet if the height of the glide path over the beginning of the full strength runway pavement suitable for landing falls within the minimum/maximum TCH values.
(2) CAT II/III. The optimum TCH is 55 feet and must be between 50 and 60 feet regardless of height group.

enter image description here Note: To determine the minimum allowable TCH, add 20 feet to the glidepath-to-wheel height and to determine the maximum allowable TCH, add 50 feet to the glidepath-to-wheel height (not to exceed 60 feet).

So, the answer to the question is ; No, they are not all 3 degrees and 50 feet.

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  • $\begingroup$ Additionally, many/most approaches do not match the 3.00 and 50 "rule" in actual practice. $\endgroup$
    – J W
    Mar 7, 2017 at 21:33
  • $\begingroup$ Incredibly useful! Thanks A LOT for your input. @JonathanWalters what kind of tolerance is acceptable. are we talking +/- 10%, or more? Table 2.1 shows, for category A a max GPA of 6.4 -- which means that you literally double the touch down distance. Surprising. $\endgroup$
    – harveyAJ
    Mar 8, 2017 at 9:34
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It almost depends on the airport location(e.g. mountain area, city), in USSR most GTA were 2.40 degrees, and for military in ex-USSR countries they are still 2.40 dergees, because they use another ground facilities.

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