PPRuNe Forums - View Single Post - Paul Phelan’s article in The Australian on Fri 10 Aug.
Old 17th Aug 2007, 04:06
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john_tullamarine
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There are a few suggestions in this thread which are a bit wide of the mark.

I note that I missed Paul's original article so I offer no comments specifically directed towards it.

The Commanders have a known set of problems which the TC holder and regulators set out to address via SBs, ADs, etc ... just like every other Type

Some general thoughts from the depths of the memory cells only -

(a) the then FAA requirement (if you wish you can review it on the FAA website's historical rules) for OEI climb differed to what the ANO required. The relevant Australian operator sought to utilise that difference to gain some extra weight and that sort of thing has been done for various aircraft over the years. My recollection is that the justification was based on structural detail comparison with larger models within the range with any non-conservative differences being addressed by mod - eg, the 500A, with which I had some involvement, had to have uprated wheels/brakes as best I recall. Models involved had to demonstrate the climb capability to justify certification aspects of the proposed weight delta.

(b) generalised references to aircraft being overweight are "correct" only to the extent that the Australian permissible MTOW exceeded the US figure. However, it must be understood that such "excess" weight was perfectly legitimate and authorised by the Australian AFM. It is very important to keep in mind that the then rules permitted local recertifications. Many were done and all required the appropriate level of tap-dancing ... DCA et seq certification folk were never amenable to being hoodwinked. When we are talking about the period and performance we are looking at eminently fine chaps such as Tenenbaum, Fincher, et al. All highly principled (sometimes to the point of being a pain in the neck). That doesn't suggest that mistakes were never made .. but the attitude and general attention to detail was always there. To suggest that the Oz regulator engineering folk were other than first rate is not supported by history regardless of what popular perception may be or have been.

(c) He was also very much aware of the fatigue issues ... Notty and I have discussed various structure cracks over the years .. he was very aware of such problems and always appeared conservative in his attitude. However, as Steve indicates in his paper, the very nature of inspection aspects of fatigue is tied up with inspectability ... ie it's a bit of a mongrel beast ..

(d) There has never been to my knowledge any meaningful flight testing done at the higher (VFR) takeoff weight 3357kg or at the higher IFR wt of 3243kg .. It would be useful for the writer to check his facts with CASA airworthiness. The basis for the Oz weights were the climb tests.

(e) the coastwatch contract .. came much later. If I recall correctly, the earlier Shrikes were used for the Navy target towing contract ? I recall a colleague relating a tale wherein the towing to simulated attack run evolution got a bit out of synch with the target retrieval ... something about the target filling up with water ...

(f) Also this category of aircraft is only required to maintain 5000' on one engine at ISA conditions. Not indicative of the aussie environment. .. misses the point. The certification requirement only puts a line in the sand. It is up to the operator's policy as to whether any further conservatism ought to be incorporated into routine operations.

(g) In June 1991, seventeen senior engineers met in Seattle . The linked paper is well worth a read for general education. Be assured that Steve Swift and Alan Emmerson, both with the Regulator and fine chaps, were very soundly versed in structural fatigue matters.

(h) The Department of Aviation never made available any flight test data or structural analysis to support the higher STC weights. .. but the data exists .. it was used to broker the subsequent 500A work. One needs to keep in mind that the Regulator has always taken the proprietary rights interests of certification data pretty seriously.

(i) The weights were challenged in 1982 when the Government Aircraft Factory’s chief test pilot . I don't recall this episode nor have I seen any related data. However, one needs to be careful that one matches the appropriate standards against the performance ? 101.22 went through several revisions (as I recall to suit some problems with which the Nomad presented). The 500S work was done to the earlier (and simpler) requirements. It is not at all inconceivable that the stated GAF tests were done to one of the later revisions ? (Note - I am not anti-Nomad, in fact quite the opposite, having worked on the beast during two separate periods).

(j) The higher weights were unilaterally taken by Australia only. ... as was quite right and proper under the regs of the time. It is only since the later regs came in that the local regulator has been tied to the NAA requirements.

(k) Probably worth noting is the fact that if the power available is just sufficient to meet the minimum performance standards with a TOW max of 6,750 lb, the additional power required to meet the same performance standard at a TOW max of 7,150 lb (Australian Certification) is 14.8% .. sounds like arrant nonsense to me. The two certification requirements were quite different.

(l) It is a serious enough deviation from the manufacturer’s limits for you to insist on a performance audit, even if it means by-passing the D.O.A. officers and going direct to the Minister. Having worked over the years with these officers may I assure readers that they were never pushovers when it came to demonstrating certification compliance. On the contrary, there are numerous instances of FOT certifications where the local regulator required additional performance tests .. the Rockwell Commander singles come to mind as an instance ..

(m) The manufacturer’s representatives expressed surprise at the certification to higher weights, and asked if somebody had fitted “a couple of turbo 350s” for the flight test. Only speculation but this comment only makes sense in terms of considering a recertification to the original requirement, not a different one ...

(n) I have not identified a single pilot who believes that an unmodified factory standard Shrike was ever able to demonstrate a 1% engine-out climb under the certification conditions at any weight in excess of 6,750 lb. .. apologies but I have so flown. The secret, of course, is that one has to define WHICH certification standard is subject to test ... certainly, the higher Oz weights could be flown to the then Oz requirement.

(o) [i]I wonder how many pilots flying the machine IFR actually recalculate their approach minima's to a height that would guarantee obstacle clearance based on what can only be argued as increadibly poor single engine climb performance?[/i] ... you mean like most other light twins of similar certification basis ?

(p) single engine climb exercise, please divulge how exactly you set zero thrust ... not relevant .. OEI tests are done shutdown and feathered.
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