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Aviation History
1963
1963 - 0345.PDF
FLIGHT International, 7 March 1963 329 COLUMH MINIMA AND MAN CEU V RABI LITY—1 PROCEEDING eastward over Trans-Jordan late one April afternoon towards the end of the war, we received a severe dust-storm report from Habbaniya, our destination, and so put down at the pipeline station H3 to refuel and await an improve ment. Shortly afterwards a colleague from the same squadron, with another transport, put down at H3 for just the same reason. After refuelling we discussed together a forecast which had just come in; it still gave very marginal weather and I decided to stay the night, using the somewhat limited facilities of the small Nissen- hutted camp. My colleague decided to press on. Over an austere supper with our Army officer passengers in the single dining room it was clear that they would have liked to press on too. In the cir cumstances I went early to bed, but had hardly undressed when there was a drone overhead, and shortly afterwards we were laying out a gooseneck flare-path to receive back the second air craft: Habbaniya, apparently, was completely "out"—and so, unfortunately, was H3 in the matter of beds for the new arrivals. It was not for nothing, I thought as I retired for the second time, that I had once been based for three years in the Baghdad area. I mention this because it illustrates in miniature the sort of com petitive pressures which have always existed in both military and civil operations in cases of marginal weather. Different pilots make different decisions; and different managements adopt different weather minima, even for the same aircraft and the same aero drome facilities. Fortunately, civil pilots these days do not often find themselves obliged to dine at a desert oasis, using the same table as their passengers; and (perhaps fortunately also) a fair number of passengers are so confused by a weather delay situation that they do not make direct comparisons between their flight and the next; but some do, and so do a great many managements. And so we find growing up a new drive to achieve regularity regard less of weather and, in default of the all-weather landing aid, an increasing tendency on the part of managements to push their minima down to the lowest common denominator. This effect is perhaps more marked in the United States than it is here for, unlike the UK, the FAA must specifically approve the minima to be applied to each operation and each aerodrome: there is therefore a fairly direct competition between the managements of the various airlines to qualify for the blue riband currently represented by jet landing minima of 200ft cloudbase and/or half- mile runway visual range (usually written 200 -£). The qualifying tests for this operation are not applied to foreign operators landing in the US, because the ICAO Chicago Convention precludes the obligatory application of operational (Annex 6) standards. But, of course, the competitive element can lead to much the same re sults: if PA A operates 707s into Idlewild at 200 - £ (as it is propos ing to do), BOAC will probably feel obliged to look at its own minima there. However, direct comparisons between companies and aircraft (even of the same genus) are particularly difficult, as will be shown in the course of these articles. In connection with the US lower-minima campaign the FAA has endeavoured to ensure a uniformly high standard of pilot training: each pilot must qualify individually for 200 - $ by demonstrating at least two ILS approaches under the hood down to 100ft ceiling, one followed by an overshoot and the other by a full-stop landing. Many pilots have successfully made this demonstration; others have not and, in a significant number of cases, a premature touch down has resulted from the go-around and a hard landing from the full-stop manoeuvre—so much so that right now there exists a widespread move among US pilots to declare the practice dan gerous. In UAL they have formally objected to the training, and the company has obtained a court injunction requiring them to accept the manoeuvres so long as they are demanded by the FAA for 200-J jet minima; contrary to some published reports, other pilots' groups (from 13 US jet operators) support the UAL pilots' stand; and so, by and large, things have got to a pretty pass. From this distance I would not presume to judge between the two schools of thought. We are dealing here with the very frontiers of human capability: we know that the pilot can land from 200ft; we know that from 50ft he needs an entirely new set of aids not yet in use; hence it is hardly surprising that there is some debate around the area of 100ft cloud base. It is a grey area and I would suggest that, before anyone resolves it into black or white, he looks closely at the fine grain. The fine grain I propose to discuss here is the margin for man oeuvre, since it appears that the basic objection to the new training requirement stems from the suspicion that, once the jet is at or near the 100ft point, the lift margin for manoeuvre is too small and that there is a fair risk that, for the overshoot case, the aircraft will not respond to elevator or speed in time to make a clean getaway. This, of course, is not a new thought, for when the jet was first introduced to line service it was widely believed that after reaching 200ft the pilot was definitely committed to land. In the circum stances of the first jets this was very close to the truth, so much so that various devices sprang up to alleviate the problem. Boeing recommended adding to approach airspeed half the reported wind and all the gust; the ARB added 8kt to the 707 and for the Comet introduced a range of permitted airspeeds rather than a single weight-derived value; others simply added an unspecified number of knots "for Mum" and hoped that they could get rid of them before running out of runway at the far end. Anyhow, by and large the pilot found a way of looking after himself. The point to note, however, is that in the introductory period pretty well all authorities told the line pilot that his qualms about the overshoot from 200ft were unfounded. But authority was wrong. Is it to be wondered at therefore, that the pilot is now mis trustful when the authorities declare the 100ft overshoot perfectly safe? Is the speed margin which was added for the 200ft case enough at 100ft in circumstances where the pilot, not at that time knowing if he is in for an overshoot or a full-stop landing, must needs have shed some of the excess speed in order not to cross the threshold too fast? The fine grain of the picture lies, I believe, in the close examina tion of these few knots. ["C.CJ."—Captain C. C. Jackson, executive secretary of IFALPA —will continue to examine this topical subject of weather minima in succeeding articles in this series.—Ed]
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