What approximate gust condition do the discrete gust amplitude and frequency values simulate?

The values of A and OMEGA simulate an approximate 15-knot gust condition.

What are the RMS intensity and scale length values for the longitudinal axis at an altitude of 700 feet?

At 700 feet, the longitudinal RMS intensity is 5.0 ft/sec and the longitudinal scale length is 950 feet.

What is the vertical RMS intensity and vertical scale length at an altitude of 1500 feet?

At 1500 feet, the vertical RMS intensity is 4.7 ft/sec and the vertical scale length is 1500 feet.

What is the approximate gust duration for a discrete gust with OMEGA equal to 0.63 rad/sec?

The approximate gust duration is 10 seconds.

What is the amplitude A and OMEGA value for the discrete gust with an approximate duration of 20 seconds?

A is 7.5 and OMEGA is 0.31 rad/sec.

Appendix 4 to ETSO-C117b - Dryden Turbulence and Discrete Gust Model

Q: What turbulence model data must be used when conducting the tests specified in paragraphs 4(d)(7)(ii), 4(d)(7)(iii), 4(d)(8)(ii), and 4(d)(8)(iii) of Appendix 1 to ETSO-C117b?

The Dryden turbulence and discrete gust model defined in Appendix 4 to ETSO-C117b must be used for those tests.

Q: For simulator altitudes outside the bounds of the Dryden turbulence table, what values must be used?

Extrapolation will not be used; simulator altitudes outside the bounds of the turbulence list will use the data at the boundary.

Q: What form of discrete gusts must be used in the horizontal axis for the Dryden model?

Discrete gusts in the horizontal axis with ranges of amplitude and frequency (A and OMEGA) of the form [A(1 - cos OMEGAt)] shall be used.

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Appendix 4 to ETSO-C117b – Dryden Turbulence and Discrete Gust Model

ED Decision 2020/011/R

This Appendix contains data that defines the Dryden turbulence and discrete gust model to be used in conducting the tests specified in paragraphs 4(d)(7)(ii), 4(d)(7)(iii), 4(d)(8)(ii), and 4(d)(8)(iii) of Appendix 1 to this ETSO.

Dryden Turbulence Model

where:

SIGMAu, SIGMAv, SIGMAw are the RMS intensities;

TAUu = Lu/VA;

TAUv = Lv/VA;

TAUw = Lw/VA;

Lu, Lv, Lw are the turbulence scale lengths; VA is the aircraft’s true airspeed (ft/sec);

PI = 3.1415926535;

PI2 = 6.2831853070 (2 times PI);

SQRT3 = 1.732050808 (square root of 3); and

S is the Laplace transform variable.

The following table lists SIGMAu, SIGMAv, SIGMAw, Lu, Lv, and Lw versus altitude. Extrapolation will not be used, and simulator altitudes outside the bounds of the turbulence list will use the data at the boundary.

Altitude (feet)	RMS Intensities (ft/sec)			Scale Lengths (feet)
Altitude (feet)	Long	Lat	Vert	Long	Lat	Vert
100	5.6	5.6	3.5	260	260	100
300	5.15	5.15	3.85	540	540	300
700	5.0	5.0	4.3	950	950	700
900	5.0	5.0	4.45	1123	1123	900
1500	4.85	4.85	4.7	1579	1579	1500

The applicant shall demonstrate that the variance of their turbulence implementation is adequate.

Discrete Gust Rejection

Discrete gusts (in the horizontal axis) with ranges of amplitude and frequency (A and OMEGA) of the form [A(1 − cos OMEGAt)] shall be used.

The following table lists the values of A and OMEGA to be used (this simulates an approximate 15-knot gust condition):

A	OMEGA (rad/sec)	Approx. Gust Duration (sec)
7.5	2.10	3
7.5	1.26	5
7.5	0.78	8
7.5	0.63	10
7.5	0.52	12
7.5	0.42	15
7.5	0.31	20

[Amdt ETSO/16]

Details

Source-Title: Appendix 4 to ETSO-C117b - Dryden Turbulence and Discrete Gust Model View latest amendments

Erulesid: ERULES-1963177438-18027 Compare versions

Domain: Initial airworthiness

Amendedby: Amendment 16

Applicabilitydate: 25 July, 2020

Entryintoforcedate: 25 July, 2020

Regulatorysource: ED Decision 2020/011/R Navigate

Regulatorysubject: CS-ETSO

Typeofcontent: CS (Certification specification)

Parentir: ETSO-C117b

Origin: EASA

Category: EAR