Remove rear seat on C172, legal?

[jkveenstra]

I was just wondering if it is legal to remove the rear seats of a C172 (EASA registered). I found a discussion on another forum, but only for FAA land: Flying with the rear seat removed - Page 2 - Pilots of America Message Board (http://www.pilotsofamerica.com/forum/showthread.php?t=1684&highlight=back+seat&page=2)

Do you need a new W&B measurement?
Would it be reasonable to ask a owner of the aircraft (flight school) to remove the seats for a trip of several days?

[7of9]

Don't see why not.

Never thought about the W&B issue, but do know a friend who owns his own PA28 & has the rear seats removed. Not sure if he has done a W&B on it.

[Pilot DAR]

Taking the rear seat out is no problem. If the aircraft is in a commercial operation, doing so should be treated as a maintenance activity, and requires a weight and balance amendment, but it's hardly complex.

Reinstalling it really should have maintenance staff oversight, and a maintenance release as it could be an occupant safety and liability issue if not documented properly.

Depending upon your national regulations, it might be an "elementary" task that the pilot can perform and sign for. If that is the case, that person is responsible for reading the maintenance manual on how to do it.

I have regularly used these aircraft as freighters, with only the pilot's seat installed.

[Shaggy Sheep Driver]

I used to do meat bombing in a 172. All seats out except the front left (mine!) and the RH door off as well.

Bluddy cold in winter, but quite legal.

[jxk]

Bluddy cold in winter, but quite legal. Are you sure it's legal without an appropriate CRS? I don't think the Cessna manuals say how this should be accomplished eg floor loading etc..

In the good old days no one would question this sort of thing but in today's environment of litigation, I'm not so sure.

[riverrock83]

From CAA website http://www.caa.co.uk/default.aspx?catid=1458&pagetype=90:
Minor and Major Modifications and Repairs

Regulation (EC) 1702/2003 (http://www.easa.europa.eu/ws_prod/g/rg_regulations.php) (Subpart D, 21A 90-97 Inclusive) contains the EASA definitions of minor and major changes.
It defines a minor change as being "one that has no appreciable effect on the mass, balance, structural strength, reliability, operational characteristics, noise, fuel venting, exhaust emissions or other characteristics affecting the airworthiness".
By default, therefore, a change is considered major if it cannot be considered minor.
Since the change will have an appreciable effect on the balance of the aircraft, I suggest that unless this is something the plane is designed to do (ie - there are instructions to do it in the hand book with a different balance schedule) then it is technically a major change, so you need to get your local maintenance shop involved.

Replacement of seats is allowed under pilot maintenance -removal isn't (at least - I haven't seen where it is!). The definitions as to mods are different in EASA land and FAA land...

Note that I'm a student pilot - so this advice is worth as much as you paid for it...

[Pace]

Your supposed to do a re weigh after a paint respray!!! Remove seats other than in a manufacturer approved basis ie they have already done calculations would mean the aircraft is illegal !

Remove the seats and its empty weight would change as well as possibly C of G moments! That would bugger up your loading calculations as well as C of G calculations as the datum would change from the published datum for the aircraft.

Pace

[500ft]

My flight school used to remove rear seats regularly. One 172 would have the seat removed to use the camera hatch for aerial photography. The other 172 was used as a back up tow plane and they would remove the rear seat when towing.

I would think you wouldn't need to re-weigh the plane, just weigh the seat. You already know the arm.

[S-Works]

My Cessna was a jump ship in its first life and still has the static line hoop on the floor. It also has a parachute ops section in the AFM and has a para config weight and balance schedule.

It's permitted to remove and replace the seats as needed and you use the relevant load sheet. It even has a jump position load sheet to make the weight and balance calculations easier.

[VP-F__]

Remove the seats and its empty weight would change as well as possibly C of G moments! That would bugger up your loading calculations as well as C of G calculations as the datum would change from the published datum for the aircraft.

Rubbish, if you remove the seat and don't put anything on the floor in that area then it will not bugger up anything, I don't recall the exact weight of a 172 seat but assuming (not that you ever should in aviation) it is 10 kgs maximum, just do the W&B calculation with a weight of -10kgs for that arm. Simples.

Removing a seat in itself is never going to kill anyone, what might kill you however is the vast amount of gear that you can get in that area should it not be suitably tied down.

[Pace]

I am being very pedantic but presuming the datums are set and the weight is set with seats installed removing them will change things even by a small amount! which maybe insignificant.
It just crossed my mind regarding strip and resprays requiring a re weigh and removing seats not? so pedantic yes :E

Pace

[phiggsbroadband]

Hi Guys, It might be easy to weigh each rear seat, but you also need to find
their C of G. to be able to do the W+B calculations. (You also need to know where the datum point is located.)

The actual C of G of the seat, because of a seat's L shape, may be located in the space between the seat base and seat back. (which is interesting.)

Removing the seats will move the plane's C of G forward, increasing the stability... Making the plane fly more nose heavy.

[VP-F__]

Pace, point taken.

For what it is worth, if the seat was to weigh 10kg or even 15 kgs and you used to moment for the seat it would move the CofG forward by about 1cm by removing the seat, not a big deal!

[Pace]

CG-F

I realize the datum point will have moved only a tiny amount but the question was is it legal?
With the idea of a miss is as good as a mile the fact that the aircraft is out of its certificated weight and balance on which all the loading graphs are based on must surely mean its not legal anymore than giving your aircraft a new coat of paint on top of the existing paint without having the aircraft re weighed ?

Yes it is as stated a very pedantic point but surely could cause a legal problem in a paperwork exercise?

Pace

[custardpsc]

At least part of the answer to this question is in the poh and I think in the equipment list for that aircraft. I had this question in an oral exam about if one could remove and fly without wheel fairings, there is a section that shows which cessna parts are R (required), O (optional) and alternatives to each other etc. This will tell you if the seat is required or not, my guess is it is optional, but not the requirements for removal or reinstatement.

The c reg 172 I fly on floats has the back seats removed so its definitely doable

[jkveenstra]

I thought there would be a single answer to my question, but it seems that it is not so simple.

Just to let you know about the background of my question. A few weeks ago I suggested to a friend to take our racing bikes on a flying trip. It can be a hassle to get these bikes in an C172 (even without the wheels). Therefore I thought about the removal of the seats. Before asking my local flying club, I just wanted to know whether it's legal or not. The seat is removed in minutes I suppose, but was not sure about the legal part.

Thanks for the discussion so far.

[Gomrath]

I think this says it all:


Don't see why not.

Never thought about the W&B issue

:ugh:

[Pace]

This puzzles me

The W & B figures and Graphs in the manual are worked out from the actual weight of the aircraft and the C of G datum point.

While I appreciate what others are saying in the fact that the datum point will only move a little it still has moved making the data in the manual null and void.
It maybe pedantic but then many things are in aviation which makes something which was legal illegal.

I have had no experience in removing seats and the technical ramifications of doing so but would imagine SOMEONE would have to approve such an action not just a pilot with a monkey wrench removing bits and pieces at will?

I appreciate in real terms it will make very little difference but in legal terms you are not operating to the certification data of the aircraft.

Pace

[Tinstaafl]

Used be a normal procedure in Oz. You were expected to calculate the adjusted EW/CG and use the new figures. That sort of stuff is included in the CPL theory exams (or used to be).

[mad_jock]

Commercially we just get a config change W&B report.

They don't re-weigh the plane just do the calcs and issue the report.

Then the W&B stays with the tech log and pilots can do the re-role with engineering QA approval. And entry is put in the techlog when ever the configuration is changed.

I can't see its a huge deal to be honest after the first time you do it.

[phiggsbroadband]

Hi, some are getting the aircraft's C of G and it's Datum Point mixed up.

The C of G position of the whole aircraft should be somewhere about 1/3 of the wing chord from the leading edge.

The Datum Point for a C172N is at the Engine Bulkhead, so very near the back edge of the engine cover.
From that point, the Front Passenger is considered to be 37 inches behind the Bulkhead, and the rear Passenger 73 inches. (i.e. they sit 36 inches apart.)

The C of G of the Seat need not be at the same position as the C of G of the person sitting on that seat, and needs to be found by experimental measurement... I remember that lesson in Physics; using Plumb-Bobs from two or more suspension points.

Best of luck... As said before, it is hardly likely to make 1cm difference overall.

[On-MarkBob]

The first thing to understand is that all fully certified aircraft types have what is known as a "Type Certificate data Sheet". (TCDS). Most are freely downloadable from the internet.
The Cessna 172 has numerous models and variants, check the TDCS is the correct one for your aircraft. The C of A and ARC are issued on the basis that the aircraft conforms to the TCDS. The TCDS for the C172 states clearly that the number of seats is 4 (2 at station whatever and 2 and station something else). To vary the configuration would mean the aircraft is no longer in compliance with the TCDS and thus the C of A is invalid.
What you have to do, is to get a qualified aircraft engineer (licenced on the type) to apply for a modification to vary the TCDS by removing the rear seat. If 'cargo' is to be carried, then the modification will have to show the provisions made for its security. Cessna already makes tie down shackles that will bolt down at the seat anchor points.
N.B. just because another similar aircraft flies about with the seat removed does not give anyone the go ahead to do similar. The modification made to the other aircraft may not be legal, or the owner might have already applied for the Mod, which is his property! so you either have to get your own Mod, or pay for someone elses!!!!

Lastly, you could contact Cessna, but be warned that even if they say its OK, that might just be for the USA under the FAA. EASA might think differently. The Mod is the way to go and be sure.

http://www.easa.eu.int/certification/type-certificates/docs/aircraft/EASA-TCDS-A.051_(IM)_Cessna_Aircraft_Model_172_and_variant-04-14042008.pdf

N.B. The Link above is for the C172R, however, some of it applies to all C172. Note under EQUIPMENT, "the basic required equipment as prescribed in the applicable airworthiness regulations (see certification basis) must be installed in the aircraft for certification"...

Rgs. Bob, EASA and BCAR Engineer + ATPL.

[jkveenstra]

On Mark Bob. Thank you for writing you comment. This is very helpful.