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Aviation History
1963
1963 - 0014.PDF
FROM ALTERNATE (1) TO ALTERNATE (2> F<t«. faAtlT. i Mot. ! Cw | TROW | VAR. | Oiit. Acc.Di«. f 5 MSA ! 10 MSA 1 20 MSA 1 :- 1 ilo 4? V>| -^v- • :,••• 40MSAJ VFR IMin.Craise Mm.Cruise Reason ! Altitude l r- -i - I V<> 4'4i +'M ?•<? 4JX. A-a 1 4-t f to.*" s-i. U-i f u-xht-UJ •- -1 M '• v| Check"",", Map Ref. Remarks U,,vioc.es fj J_ --fSi»i_©i)S& ^Aft^-A^a^S! i)e/<PiO.Kn.M. 1 HT-G>«C»^U ^V\^V ^\^S^, 14 FLlGHl Internal 3 Januct 1963 ._._ 1 J u : <-J 4.S jM *?•;> iM-j ad ** feL r a'-5 iM -> //•*|//-y <n,)k(,cS« V&dP' ti I^ fttvj , k-iHo^cS I ftgii "feu^i^c fL*C?«<3.M(V»i I 4- -r T -i—I- Method of using Minimum Safe Altitude tables, explained in the text below SAFETY HEIGHT . . . Minimum Safe Altitude Tables (see illustration) Five-mile MSA This provides (1) 1,000ft clearance either side of the airway centre line (width of an airway) and five miles beyond the terminal points over all flat terrain and obstructions and (2) 2,000ft over designated mountainous terrain as defined by ICAO. This is to be used :— (1) when flying VFR (2) when operating on an 1FR flight-plan but in VMC conditions and at least 1,000ft on top (3) IFR under positive radar control. Ten-mile MSA This provides 2,000ft clearance above all known terrain ten nautical miles either side of the intended track and ten miles beyond the terminal point. This is to be used:— (1) when arising on an IFR flight plan under IMC conditions (2) when the actual or forecast wind is not more than 25kt and (3) when the aircraft has one serviceable VOR plus one service able ADF or (4) when the aircraft has two serviceable VOR receivers and (5) when the aircraft is within 80 miles of a VOR ground station which is being clearly and unmistakably received and is in line with the intended track and (6) when the aircraft has the simultaneous use of two independent ground radio aids. i.e., (a) when the aircraft is tuned into and is utilizing a VOR at the destination or the next reporting point for track guidance plus an ADF in the vicinity of the VOR, or (b) when having only two VOR ground stations available, one being utilized for track guidance and the other for obtain ing ground speed checks, or (c) homing along the intended track using one VOR and obtaining ground speed checks from the ADF. In no circumstances is (6) to be construed as meaning the use of two airborne receivers on one ground transmitter. Twenty-mile MSA This provides 2,000ft clearance above all known terrain 20 nautical miles either side of the intended track and 20 miles beyond the terminal point. This is to be used:— (1) when cruising under an IFR flight plan in IMC conditions (2) when the actual or forecast wind is more than 40kt (3) when the aircraft has two serviceable ADFs or (4) when the aircraft has one serviceable VOR and (5) when the aircraft is within 80 miles of well received and static-free ground stations, one of which must be in line with the intended track, and (6) when there is available the simultaneous use of two ground fixing aids. i.e., (a) one ground NDB being utilized for track-holding and the second NDB for ground-speed checks, or (b) the serviceable VOR for track-keeping and switched for short periods on to a second ground station for the purpose of obtaining ground-speed checks. Forty-mile MSA This provides 2,000ft clearance above all known terrain 40 nautical miles either side of the intended track and 40 miles beyond the terminal point. This is to be used:— (1) when operating under an IFR flight plan in IMC conditions (2) when the actual or forecast wind is more than 40kt (3) when the aircraft has only one serviceable ADF or (4) when the aircraft is more than 80 miles from a ground trans mitting station or (5) when no ground radio aid lies along the intended flight path. The use of ILS in place of VOR for track-holding and ground- speed checks will be acceptable in the above MSA definitions, e.g., utilizing Geneva ILS for tracking between Sottons and Passeiry. The reason for using a constant 2,000ft clearance over known terrain is that the majority of topographical maps do not carry a systematic revision service so that the assumption must be made that, since publication, a 1,000ft TV mast may have been erected on the highest terrain; this is usually the case. A further 1,000ft maneuvering clearance is required, giving a total of 2,000ft. Over mountainous terrain at least 2,000ft is required to counteract down-draughts and altimeter errors due to local pressure variations induced by wind circulation around the mountains. For winds in excess of 40kt an additional 1,000ft should be added to the 2,000ft and this figure increased with the wind strength so that an addi tional 4,000ft is required for winds in excess of 80kt. No MSA should be accepted unless this height can be main tained in the engine out configuration or the terrain cleared by a power glide. When constructing a 40-mile-wide safety lane, the MSA 25 miles either side of track must, of course, be considered to cover the case of an aircraft flying on one of the edges. In this position it must still have a five-mile clearance over all terrain to conform with ICAO recommendations. This is called a 20-mile MSA. It will be noticed that emphasis has been placed on high-fre quency aids for the narrower safety lanes and that when low-fre quency aids are used static-free conditions are mandatory. Dupli cation of aids must obviously produce the most economic use of air space; this is especially so if some form of mechanical navigator such as Decca is monitored by an HF aid such as VOR/DME. To sum up: present topographical maps are inadequate for modern requirements while the lack of a systematic revision service makes their continued use a potential hazard. It is my considered opinion that terrain and obstruction information should be precied by experts and the results repeated on radio facility charts Legis lation should be introduced to ensure that each pilot receives by the third week of each month amended radio facility charts which become effective at OOOlhr on the first day of the following month Actual winds and airport weathers should be continuously avail able to the pilot in flight. The responsibility for the provision of this mformation should be accepted by the State. The criterion to be met is the safety of the most inexperienced pilot on his first route flight.
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