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## Removing Seats in Echo Aircraft

• Posts: 17

### Kaos created the topic: Removing Seats in Echo Aircraft

Howdy,

Whilst working through your Echo questions I've noticed that several state the seats are removed. Seats weigh 5kg each so by removing them the index units need to be adjusted accordingly - Ie removing 2 seats (10kg) from say Row 3 means subtracting 4.3 index units from the final figure.

I have seen plenty of questions calling for the seats to be removed but there doesn't appear to be any adjustment for this in the answers. Is this just an oversight? Removing seats from all 3 rows (except pilot seat) changes weight by 25 kg and about 9 index units - this will significantly alter our answers.

Hoping you can provide some insight as I want to make the correct calculations next week when I sit the exam

• Posts: 16

### hews16 replied the topic: Removing Seats in Echo Aircraft

Hey Kaos,

Student thoughts here:
My observations from doing the PEXO exam is it will depend on what type of weight is given i.e. BEW vs Gross Weight attached to the weight in your question.

CASA's particular tricks are to give you a "gross operating weight" in the first line of the question and then later on in the question, they mention that seats have been removed. The trap is to see if you will remove the seats again, which you shouldn't.

My approach was this: if e.g. gross operating 2300 weight is given, and seat data given later on, ignore it, as gross operating weight would mean all adjustments relating to the aircraft load have been made. Another trick I saw is the questions saying "aircraft is loaded for takeoff at 2300KG" or "operating weight of 2300". All these are GROSS WEIGHT, post adjustment.

If (Basic) Empty Weight is given, and then seat data also given, it is you who will have to make the adjustment.
The following user(s) said Thank You: sean1390

• Posts: 17

### Kaos replied the topic: Removing Seats in Echo Aircraft

Awesome thank you! I thought they might do it like that, our flight school haven't been as kind which is why I thought I'd ask haha.

Appreciate it mate!

• John.Heddles
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• ATPL/consulting aero engineer
• Posts: 332

### John.Heddles replied the topic: Removing Seats in Echo Aircraft

I haven't seen any of the exam questions to which you refer - mine were done a long time before any of you probably were born.

(a) in the absence of a configuration definition of what a particular defined weight configuration might be, you can't just dream up your own.

(b) the only exception (to some extent) is "empty weight", which is described in the CAOs. I say "to some extent" as the CAO definition doesn't cover all bases out there in the real world.

That is to say, if the question refers to some sort of weight configuration, the question, somewhere, needs to define that configuration - or the examiner needs to have defined it somewhere else for student reference. Otherwise all is a bit silly.

Generally, empty weight will be as per the CAOs and the WCO will define one or more basic or operating weights in the load data sheet for pilot operational use. If you don't have the LDS (or similar exam) information, then you run up against a brick wall.

Certainly, if the starting weight data includes seats, and you propose to remove them, you will need to adjust both weight and CG (or IU/moment). However, you have to have a defined starting point to make any sense of it all.

Engineering specialist in aircraft performance and weight control.

• Posts: 1902

### bobtait replied the topic: Removing Seats in Echo Aircraft

I think you will find that the questions you refer to are saying that the total weight and moment given are for the aircraft AFTER the seats are removed. If you have removed the seats, of course the weight and moment would have changed as you describe. Since the basic empty weight given in the flight manual has a very specific definition and includes the seats, the condition with the seats removed is no longer the basic empty weight. It is variously called the 'operating weight' or the 'aircraft prepared for service weight'. In most of the CASA questions I have heard of, the figures given reflect the condition after the seats have been removed.

So the text of the question should make it clear whether the weight and moment given is the basic empty weight or the operating weight.

• John.Heddles
• Offline
• ATPL/consulting aero engineer
• Posts: 332

### John.Heddles replied the topic: Removing Seats in Echo Aircraft

A bit of amplification to Bob's post -

The relevant Orders are

(a) CAO 100.7 www.legislation.gov.au/Details/F2018C00475 which controls what the maintenance/engineering/WCO folk generally do. This includes a definition for empty weight and a generic description of what is included in operating weight.

While you are extremely unlikely to get any exam questions relating to 100.7, pilots should be familiar with its content. In practice, the LDS (or the relevant POH pages for light aircraft if an LDS is not raised) will ALWAYS prescribe an empty weight and, generally, some additional configurations which can be called whatever the operator/WCO decide in conjunction. Very often, you might find a list of configurations covering different operating scenarios required by the operator. Hence, it is ALWAYS important to read what the LDS (or exam) might say in regard to configuration control. Particularly for multi-purpose aircraft operations, it is not at all uncommon to see 5-10 different operating configuration data sets, regardless of what they might be called. The main reason for this is to avoid the error potential of having the pilot do the sums for each flight configuration change as appropriate. Often these different configurations will reflect different seating arrangements for different operational requirements. Very commonly, you will see a full seating configuration and a freighter pilot seat only configuration, for instance.

Whether you see references to basic weight, operating weight or other fanciful expressions is in the lap of the Gods. As a side-note, APS data generally will be seen only for heavy aircraft.

(b) CAO 20.16.1 www.legislation.gov.au/Details/F2018C00462

(c) CAO 20.16.2 www.legislation.gov.au/Details/F2005B00989

(d) CAO 20.16.3 www.legislation.gov.au/Details/F2009C00628

The 20.16 Orders MUST be known by the pilot fraternity and are fair game for the examiner to question in the exams.

Engineering specialist in aircraft performance and weight control.