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Merchantman onboard trim indicator

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Merchantman onboard trim indicator

Old 22nd Apr 2021, 22:06
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Merchantman onboard trim indicator

There is an article in the latest Propliner annual about a day out aboard a Merchantman and it mentions a device fitted aboard to make sure that the aircraft was within its operational envelope. I have not heard of this before so would appreciate an explanation of it from anybody familiar with it.
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Old 22nd Apr 2021, 22:54
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This was the STAN system to measure the weight and centre of gravity of the aircraft. STAN stood for SumTotalAndNosegear IIRC

The system worked by measuring the oleo deflections on all three gears. The aircraft was taxied for a short distance with take-off flap set and then stopped and the switch was held on until the reading appeared. It was used to verify the loadsheet and was not very reliable. A similar system was used on some early B747Fs.

The scope for misloading on freight aircraft is quite great compared to passenger aircraft. Usually it's pallets loaded in an incorrect order - therefore total weight OK but c.g. out.
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Old 22nd Apr 2021, 23:56
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Meet STAN.
This one is for a B707-300.



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Old 23rd Apr 2021, 03:47
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A similar system was used on some early B747Fs.
Meh think it was an option on Classic 747 pax and combi birds.
I flew some in the sandbox that had every option in the catalog, not only the weight and balance readout, but also Cat III, no glass only steam gauges and 3 autopilots, decision height 20’ and your were supposed to touch down during a missed approach, then take off again to complete the missed.
Analog magic, I am telling you.
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Old 23rd Apr 2021, 17:29
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I think all freighters should have something like this. With modern tech it should be quite possible to make it reliable.
We lost two good guys on an F27 at GCI due to an out of trim aircraft and there have been quite a number of others. Fine Air at Miami for one.
I think the bean counters don't like it as you would have quite a few returns to stand for just a minor error.
Actually why not on pax a/c as well. There has been a duscussion about standard weights for pax lately. This would solve the problem.
Once the aircraft is rolling the oleo pressure is directly proportional to the weight being supported, simple sums comes up with a Go/NoGo answer.
Sorry for thread drift, but this bugged me for all my years in air cargo.
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Old 23rd Apr 2021, 17:31
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Did STAN have any head or tail wind limitations?

I've been involved in weighing light aircraft and gliders for CG purposes and it is always done in a closed hangar, to avoid erroneous readings caused by wind.
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Old 23rd Apr 2021, 18:26
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I42: I think it had to be done with the aircraft stopped "crosswind".
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Old 24th Apr 2021, 22:31
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Thank you for the replies. I can thoroughly recommend the Propliner annual in which the article about the Merchantman appears. I have seen reference in the manuals for the A300-600 to a similar optional system but not the technical detail.
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Old 25th Apr 2021, 11:24
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I was a despatcher for Merchantmen in the mid 80s (Air Bridge Carriers) and can confirm they had this. The captain would wait until taxying in case the oleos were sticking - a few brake applications sorted it out. We were very strict on loading pallets and igloos - they went over a weighbridge and we didn't trust TNT to tell us the correct weight. In a couple of years we only had one come back on stand with the trim being out - can't remember the outcome as to whether it was real or an instrument problem (but I didn't do the load-sheet on that one!). We had it drummed into us that if the aircraft went down into Lough Neagh, our names were on the load-sheet.
With today's technology it should be really easy. If the "typre pressure monitoring system" on cars can read the difference in circumference of a deflated tyre vs a fully inflated one, I'm sure an oleo measuring system could take three measures and work out actual take-off weight and trim CG.
I agree with other posters there have been fatalities due to mis-loading and this should be a simple option, compulsory for freighters.
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Old 25th Apr 2021, 13:41
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Originally Posted by dixi188 View Post
I think all freighters should have something like this. With modern tech it should be quite possible to make it reliable.
We lost two good guys on an F27 at GCI due to an out of trim aircraft and there have been quite a number of others. Fine Air at Miami for one.
I think the bean counters don't like it as you would have quite a few returns to stand for just a minor error.
Actually why not on pax a/c as well. There has been a duscussion about standard weights for pax lately. This would solve the problem.
Once the aircraft is rolling the oleo pressure is directly proportional to the weight being supported, simple sums comes up with a Go/NoGo answer.
Sorry for thread drift, but this bugged me for all my years in air cargo.
Dixi, i feel i must point out, without any bad will towards the two lost pilots in the Channex crash in GCi the following:-
TheFO prepared a perfect load sheet shoeing the loading of the aircraft.
The loaders at Luton, having never loaded an F27 before, asked the Captain how the nrwspapers should be loaded. He replied "start from the back and move forward. That"s what put the aircrafy out of trim.
https://assets.digital.cabinet-offic...000_G-CHNL.pdf
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Old 25th Apr 2021, 23:41
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Originally Posted by bean View Post
Dixi, i feel i must point out, without any bad will towards the two lost pilots in the Channex crash in GCi the following:-
TheFO prepared a perfect load sheet shoeing the loading of the aircraft.
The loaders at Luton, having never loaded an F27 before, asked the Captain how the nrwspapers should be loaded. He replied "start from the back and move forward. That"s what put the aircrafy out of trim.
https://assets.digital.cabinet-offic...000_G-CHNL.pdf
I hear what you are saying and there were deficiencies in the training at the time, but a STAN system would have saved the day.
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