HIC and setback 1

[Svorek]

Hi,

I'm engineer in a company in France which provides modification and certification on aircraft.

For a Cabin Modification on an Emb175, we installed a table in front of a VIP Seat.

We place the table in accordance with the Seat Install Manual :
I quote :
" For double seat, installation aft of any monument must have a minimum setback of 22.86" in case no HIC substantiation is available. For Setbacks below 22.86", installer must provide substantiation for 14 CFR 25.562(c)(5) compliance. This setback accounts for the 50th %ile ATDs"

So we kept a setback of 24" for the installation.

But, when we sent our certification program to EASA, we receive this answer :
"The supporting data they obtained from the seat manufacturer lists a set-back for seats behind interior installations (use for front row seats). The data is only covering 50%tile occupant size. The seat behind a table is not accepted as a front row seat. The clearance shown in the drawings is 24 inches while the minimum acceptable would be 25.86inches."


Can someone explain me why should we take a setback 3"-superior to the setback in the Installation Manual ?

What are these 3" ??

Thank you.

 

[rb1957]

difference between the 50%-ile and the 95%-ile (or 90% or 99%)

Quando Omni Flunkus Moritati

 

[Svorek]

Thank you for your answer, but how can we know if we can use the 50% tile or if we have to use the 95% tile ?

Why whould we use the 95% tile for this installation ?

And as we have only the setback for the 50% tile, there is a regulation which says we have to add 3in ?

Thank you.

 

[rb1957]

1) your regulator wants you too.

2) it might be defined in the EASA ACs.

3) it is why you talk to your authority before you complete the project (the cert. plan is there to make these rulings ahead of time, so you don't get surprised.

4) using the 95%-ile (or whatever) is probably defined in the AC.

5) you can always placard the seat "suitable for passengers less than X'(Ym) tall".

Quando Omni Flunkus Moritati

 

[rb1957]

the FAA's AC addressing 25.785 (AC25-17A), some 800+ pgs long !, shows a required 35" radius, fig81-2, pg 47.

this may or may not help with EASA. EASA should have their own guidence material.

Quando Omni Flunkus Moritati

 

[rotw]

They replied that "The seat behind a table is not accepted as a front row seat."

Means if your case would have been accepted to fall under "front row seat" category you might be fine with 24" as per installation manual clause you quoted. But because it is behind table the quoted paragraph does not apply and you should fall into another clause, which by the way you should look for in the installation manual, that dictates a different requirement, namely the minimum of 25.86".

I am not from the field at all, so pardon me if my answer is not relevant.
Just tried



"If you want to acquire a knowledge or skill, read a book and practice the skill".

 

[MintJulep]

http://www.ecfr.gov/cgi-bin/text-id...e7077423a680556e&node=se14.1.25_1562&rgn=div8

The cited section of the CFR requires substantiation and test with a 50% percentile test dummy. You have provided data accordingly.

Challenge the ruling.

 

[rb1957]

the only mention i see for "dummies" in 25.562 is for testing the seat for dynamic loads (para b).

The AC defines very specifically the head strike zone.

this is all FAA ... EASA has their own take on things. "challenging the ruling" is like "arguing with the wifereferree" ... "i disagree. sure, disagree, but i'm not changing my mind". but you can ask how they came up with such a specific dim'n. (i think 3" is the difference between 50%-ile and 9x%-ile)

Quando Omni Flunkus Moritati

 

[der8110]

The FAA and EASA will be remarkably similar on these regs. The 3" is indeed the difference between the 50th percentile male dummy as tested and the 95th percentile male for which HIC compliance must be shown. See policy memo ANM-115-05-14. HIC compliance must be shown for the 5th percentile female through 95th percentile male, though the smaller individuals are rarely critical. This is not surprising since the rest of the cabin has to show compliance for the same occupant size range (ordinance sign visibility, oxygen mask presentation, etc.)

Both the 25.562 head trajectory and 25.785 35" arc must be complied with, they are often confused together.

 

[Svorek]

Thank you for all your answer. I will look with the AC25-17A what says the text.

By the way, we have move the table forward, but for my personnal knowlegde, I search the reason for it.

 

[Svorek]

Hello,

I am back to you with an answer, and another question about HIC.

Concerning the 3 additional inches : on AC25-562-1b (page 48), it is mentionned " Adding 3 inches to the 50th percentile ATD head path is typically acceptable to account for the 95% occupant head path".

I don't have yet read all the Advisory Circular, but it is a first answer.

Then, a new question now.

I have to install a FC Seat on an Embraer 135. In the seat install manual, there is many case shown with setback, but the case "Forward Facing Seat aft a Monument higher than 17in" is not shown.

So, I can't install my seat aft a wardrobe or a galley in my aircraft.
I'm forced to install my seat Aft-Facing.

Is it possible to justify a position with the headpath given in Install Manual or cases not shown in Install Manual is simply not allowed.

I'm surprised that a seat can be forbidden in this position.

Thank you.

 

[rb1957]

there's quite some material on the FAA site, search "aft facing seat". AC25.785-1b

another day in paradise, or is paradise one day closer ?

 

[der8110]

First, check the data plate on the seat to see if it is rated "forward facing", "aft facing", or both ("forward/aft facing"). The install manuals (IIL) are often written for a family of seats, which can include forward facing, aft facing, singles, doubles, triples, etc.

The setback dimension should not limit what type of monument is placed in front of the seat. If it's an aft-facing seat, then there will have to be some necessary space to allow for deformation, unless you want to experience the fun of load sharing.

If you have a headpath applicable to your seat, then you are pretty far ahead. It's pretty rare to get those for airliner seats. Also check that it does not conflict with setback dimension ("applicability"). Some seat manufacturers, unfortunately, charge extra for data to support alternate installations. So you might be forced to pony up more money and incorporate a service bulletin to install a new data plate, change the dash number, etc., and not do any significant changes to the seat. Their right, I guess.