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Aircraft Trim Sheet loading

  • John.Heddles
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John.Heddles replied the topic: Aircraft Trim Sheet loading

Much the same, in the way of comments, as for the Warrior sheet. Pretty poor quality and not of a standard meeting the absolute minimum for approval.

Specific comments -

(a) the sheet has no design provenance or regulatory approval for use as a loading system

(b) the tabulation has no provision for zero fuel weight. What is even worse, the order of the trim lines makes it needlessly difficult to run a ZFW check. You can do it, but you would need to run the seat rows, then the baggage lines for the ZFW case .. and then run back up to the fuel line for the TO case. Dreadful.

(c) as with the earlier sheets, there is no information relating to the entry IU other than an isolated mark.

(d) the IU divisions in the trim lines are not clearly defined at the RHS of the lines. Again a potential source of error.

(e) the baggage lines have no indication as to the weight increment and are unusable. (The number missing is 10kg for both).

(f) the fuel IU change is not a decimal quantity. As with the other sheets, there is no provision for SG input which, necessarily, sets one up for error. (As with the Warrior sheet, the line is drawn for an SG of 0.71)

(g) the sheet datum is the OEM datum. As such it is inappropriate as the error in completing the trim sheet is higher than it need be. A better datum would be somewhere inside the envelope so that the envelope, as drawn, is an upright, boxy shape.

(h) the IU change lines are based on kg. The envelope is based on lb. Errors waiting to happen.

The sheet is not valid for approval and use in operations.

Engineering specialist in aircraft performance and weight control.
#41

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  • ray9ed
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ray9ed replied the topic: Aircraft Trim Sheet loading

How did you work out what the missing values from the trim sheet were ? I'm looking at the baggage line weights and the fuel sg.
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  • John.Heddles
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John.Heddles replied the topic: Aircraft Trim Sheet loading

As for figuring out most things when one starts with the final product .. reverse engineering.

By this I mean that one knows the generic equations and so forth. Either by comparing the end result to other, available information or making some educated guesses, usually it is not terribly difficult to figure out how the end product has been achieved.

Specifically,

(a) for the baggage line, we know arm and delta IU so it is straightforward to figure the missing delta weight

(b) for the fuel line, similarly, we can figure the delta weight which, with the volume, allows us to figure the SG.

I will leave it at that .. while this thread is of general use to up and coming pilots (by virtue of its being able to alert folk to things of which they should be aware and looking out for) .. it goes way beyond the site's remit. Bob has been very indulgent in allowing this thread to have a free rein. However, I don't think we ought to go too far from the basic familiarisation idea.

Engineering specialist in aircraft performance and weight control.
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  • dave.lynne
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dave.lynne replied the topic: Aircraft Trim Sheet loading

Longtime lurker and now registered. I have been following this thread for some time as I have always had difficulties with trimsheet calculations. I have a copy of a B200 trimsheet which appears to show some of the errors you have described in earlier posts although it is approved by a well-known weight control authority holder. Are Kingairs in your line of interest ?
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  • John.Heddles
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John.Heddles replied the topic: Aircraft Trim Sheet loading

a B200 trimsheet which appears to show some of the errors you have described in earlier posts although it is approved by a well-known weight control authority holder

This is my aim with this thread .. to get folks to the stage where they have a reasonable idea of what they should be seeing in a loading system (specifically trimsheets) and have the confidence to query anything which doesn't look quite right.

A problem with the present WCA system is that CASA, and its antecedents, looked only at aircraft weighing and simple loading systems .. but then permitted the WCO essentially free rein with whatever loading systems he/she might choose to play. As a consequence, there are quite a few WCOs out there who dabble in complex loading systems without knowing quite what they are doing .. and get things dreadfully wrong at times.. Fortunately, CASA has flagged an intention to look at, and fix, inter alia, such problems.

Suggest you follow the trend of this thread, remove identification of operator and WCO and post the sheet. I can review it and then post a critique.

Are Kingairs in your line of interest ?

Loading systems are all much of a muchness. The only real differences between a trimsheet for a C150 and a B747 is the amount of detail and overall complexity ... the basics are much the same for both.

C150, B200, B747 .. bring them on .. providing I have access to necessary data, I can review and critique.

Engineering specialist in aircraft performance and weight control.
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  • dave.lynne
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dave.lynne replied the topic: Aircraft Trim Sheet loading

Trim sheet is for King Air B200 VH-ZXM. As I read it, the CG envelope looks to be in CG units rather than IU.
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  • John.Heddles
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John.Heddles replied the topic: Aircraft Trim Sheet loading

Well done, that man. Parallel sides on the CG envelope in a trimsheet are an instant red flag.

It is premature to say that the sheet is in error as there is a small possibility that the envelope shape could be the result of an error analysis and subsequent curtailment process .. not all that likely, but possible .. ergo .. we need to run a reverse engineering exercise to see what might be hidden in the sheet design detail.

Give me a few days to fit that into the program and I shall return with some critique details.

Engineering specialist in aircraft performance and weight control.
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  • John.Heddles
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John.Heddles replied the topic: Aircraft Trim Sheet loading

I've now had time to undertake a preliminary review of the sheet and it appears to have a number of significant errors/variations from what one would expect to see.

As the aircraft is a pretty complex twin turboprop and, apparently, operated by a reputable AOC organisation in high end VIP/charter operations, I would prefer to report on a detailed critique. Please do allow me a few more days to finalise my review.

What really astounds me is that, for such an aircraft in such operations, and subject to routine serious CASA audits ... the CASA FOIs and AWIs involved have not picked up on the obvious red flags associated with the envelope presentation (as has the previous poster). While one wouldn't expect the CASA field folks to have the skills to do the detailed engineering assessments (although there is no reason why they couldn't have those skills), they should be acting as the front line coalface filter (similar to the local medical GP) and referring higher level problems to the specialists (in CASA's case the operations engineering SME folks) who are every bit as able as I to tease out the problem details .. not to mention the fact that they can interact with the relevant operator and WCO. Perhaps there is a need for some additional training at CASA field level in weight control or, as the pilot folk would put it, aircraft weight and balance control.

Again, thanks to the poster for de-identifying the sheet .. it is not this site's role to play policeman or embarrass anyone .. our interest should remain that of educating Bob's student body (and any other interested readers).

Engineering specialist in aircraft performance and weight control.
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  • John.Heddles
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John.Heddles replied the topic: Aircraft Trim Sheet loading

Now had time to review the sheet in reasonable detail.

As suggested earlier, the entry line numbers and the envelope relate to the CG envelope (as CG length units) rather than the moment envelope (as moment units).

Further, the individual trim lines (from which one can infer the IU equation), are variable in their precision and accuracy. While I cannot be certain of the reason for this, it is suggestive that the designer of the sheet, rather than design it from scratch, has co-opted sheet data from another aircraft with a similar, but not identical, seating layout - that's my speculation.

Why the mix and match (entry argument and envelope in CG units and the remaining trimlines in IU units) is beyond me totally .. it just doesn't make any logical sense.

The sheet should not have been approved and should not be used operationally.

You have indicated that the sheet has been approved by a reputable WCO. I probably would incline (hopefully incline ?) to the view that the sheet was designed by someone else for checking and approval by the WCO who, unfortunately, has not been adequately diligent in his/her checking protocols.

Engineering specialist in aircraft performance and weight control.
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  • ray9ed
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ray9ed replied the topic: Aircraft Trim Sheet loading

I have a problem with these errors and the associated discussion. For the small aircraft, it may be just a case of pilots not completing the chart and just guessing the weight and balance situation before going flying.

However, the King Air is at the other end of the market and flown by experienced, professional pilots within a disciplined training and checking system overseen by regular CASA audits. Surely these pilots are completing the trim sheet? If it is no good, why aren't they finding difficulty getting it to work and raising questions within their operations management system?

Something does not gel, here.
#50

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