Removing one of my rear seats in the Cherokee 140

CC268

CC268

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CC268
Got a 1965 Cherokee 140 - my dad and I have discussed removing the rear bucket seat behind the pilot side as it will essentially never get used. We would leave the one that is behind the passenger seat. A few snaps in front and two fasteners in the rear removes the bucket seat I believe.

Would have to have a new W&B done. What about a 337 form?
 
CC268 said:
Got a 1965 Cherokee 140 - my dad and I have discussed removing the rear bucket seat behind the pilot side as it will essentially never get used. We would leave the one that is behind the passenger seat. A few snaps in front and two fasteners in the rear removes the bucket seat I believe.

Would have to have a new W&B done. What about a 337 form?
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For my '66 PA28-140, I had two W&B made up, one for with rear seats, one for without. My A&P said no 337 is necessary. I once let someone convince me that my A&P was wrong, but I then confirmed it by checking with my local FSDO and they agreed: no 337.
Because my seat bottoms Velcro in, I made up two carpet-covered "panels" that I Velcro down on the floor once the seats come out. It turns my Cherokee into a flying station wagon. The panels are just 1/4" plywood, with a black carpet attached to one side (the "up" side) and Velcro on the bottom (the down side). They are reinforced on the bottom with more 1/4" plywood runners full length... and they about 4 inches longer than the rear deck that the rear seats attach to, making the back very clean and neat when the seats are removed (the plywood runners lift the panels up off the deck a tiny amount, just enough to hide the seatbelts and seat back attachment points). When I put my panels in, you would swear my Cherokee never had back seats in the first place, and the panels are very light, weighing just 6 lbs. I'll dig through my photos tonight when I get home, as I'm sure I have a picture with the rear seats removed.
 
tawood said:
For my '66 PA28-140, I had two W&B made up, one for with rear seats, one for without. My A&P said no 337 is necessary. I once let someone convince me that my A&P was wrong, but I then confirmed it by checking with my local FSDO and they agreed: no 337.
Because my seat bottoms Velcro in, I made up two carpet-covered "panels" that I Velcro down on the floor once the seats come out. It turns my Cherokee into a flying station wagon. The panels are just 1/4" plywood, with a black carpet attached to one side (the "up" side) and Velcro on the bottom (the down side). They are reinforced on the bottom with more 1/4" plywood runners full length... and they about 4 inches longer than the rear deck that the rear seats attach to, making the back very clean and neat when the seats are removed (the plywood runners lift the panels up off the deck a tiny amount, just enough to hide the seatbelts and seat back attachment points). When I put my panels in, you would swear my Cherokee never had back seats in the first place, and the panels are very light, weighing just 6 lbs. I'll dig through my photos tonight when I get home, as I'm sure I have a picture with the rear seats removed.
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Sweet thanks!
 
Walboy said:
I wouldn't reweigh the airplane. You know the weight, you know the arm, therefore you know the change in moment. It's basically a negative weight passenger in that seat. Recompute the CG and if it's in the envelope, you're good to go. Use the new total weight and moment that YOU determined for computations going forward. If you reinstall the seat, then reverse.

What I would do is have two spreadsheets with and without the seat and keep it with the flight manual. This keeps it simple and you can show the FAA if you're ramp checked.
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Yea that is exactly what I was going to do
 
Don't forget that weight and balance needs to be entered in the logbook by an A&P.

Bob
 
Walboy said:
I'm not being argumentative, I'm trying to study up. Could you please cite the FAR that requires this in the case removing a removable seat?
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Any change of one pound or more requires a new Weight and Balance, which can only be created and logged by an A&P. These are two FARs that are relevant.

§43.5 Approval for return to service after maintenance, preventive maintenance, rebuilding, or alteration.
c) If a repair or an alteration results in any change in the aircraft operating limitations or flight data contained in the approved aircraft flight manual, those operating limitations or flight data are appropriately revised and set forth as prescribed in §91.9 of this chapter.

§91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards…
 
That sounds like a misapplication of a maintenance requirement to me. It is neither maintenance or permanent alteration. The airplane is designed for removal of the seat. Burning one gallon of fuel would have more impact on the airplane than removing the seat. I think as long as you go to the effort to adjust your W&B as Walboy suggested, I don't think any inspector would have an issue with it.
 
The conservative approach to this is if the airplane manual has numbers for the seat removal (doesn’t matter if it was *designed* to be removed, matters if the manufacturer *documented* that it could be removed and what to do to W&B calcs when you do) you’re okay to do the calcs from manufacturer data and fly it.

If the manufacturer didn’t provide numbers, then you get a second W&B done by an A&P and keep it with you for those times the seat has been removed.
 
Walboy said:
I'm not being argumentative, I'm trying to study up. Could you please cite the FAR that requires this in the case removing a removable seat?
Click to expand...

I didn't take it that you were. The rules are confusing for a&p's too.

There is no specific far requiring it. You are required to operate the aircraft within limitations of the type certificate. You cannot comply with that without knowing the true and current weight an cg. Here is a good post from another forum discussing it.


There is no blanket requirement in the regs that this information be carried aboard the airplane. However, under the section "AIRPLANE FLIGHT MANUAL AND APPROVED MANUAL MATERIAL"

§ 23.1589 Loading information.
The following loading information must be furnished:
(a) The weight and location of each item of equipment that can be easily removed, relocated, or replaced and that is installed when the airplane was weighed under the requirement of § 23.25.
(b) Appropriate loading instructions for each possible loading condition between the maximum and minimum weights established under § 23.25, to facilitate the center of gravity remaining within the limits established under
§ 23.23.

Combine the above with 14 CFR 21.5, which says

21.5 Airplane or Rotorcraft Flight Manual.
(a) With each airplane or rotorcraft that was not type certificated with an
Airplane or Rotorcraft Flight Manual and that has had no flight time prior to
March 1, 1979, the holder of a Type Certificate (including a Supplemental
Type Certificate) or the licensee of a Type Certificate shall make available to the owner at the time of delivery of the aircraft a current approved Airplane or Rotorcraft Flight Manual.


and combine that with 14 CFR 91.1 which says

§ 91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.
(b) No person may operate a U.S.-registered civil aircraft—
(1) For which an Airplane or Rotorcraft Flight Manual is required by § 21.5
of this chapter unless there is available in the aircraft a current, approved Airplane or Rotorcraft Flight Manual or the manual provided for in § 21.141(b);

All of the above applies to aircraft with no flight time prior to March 1, 1979. Prior to that, some aircraft had as part of their type certificate that current weight and balance information be carried aboard the aircraft, or had a requirement for an AFM.

Bob
 
Let's say the rear seats are easily removable, but no mention is made in the POH.

Here's a couple of potential issues...

1) With the seat removed, how much weight can the floor beneath the seat support? Is is NOT safe to assume the same amount as the seats themselves - their weight is usually concentrated on specific structure.

2) Was the strength of the seat hardware included in the calculations of fuselage strength?

Of course, one can guess. But stick a few hundred pounds of machine parts back there and then pull 3g's - it really is a guess if the floor will deform under a 900lb load, and if it does, whether any cable or wiring routing will be compromised.

Cirrus owners faced this issue, and at least one company responded with an STC'd product: http://cirrus.tamarackaero.com/cargo-conversion-2/

As usual, owners are free to do as they choose, and very likely will not ever face legal or safety issues just playing it by ear. But then again...
 
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Great question and something I’ve pondered but never fully explored.

What does an aircraft weigh cost on average/ballpark?
 
Following on FastEddieB's comments...its not just W&B. On a cherokee 180, max weight in the baggage area is 200 pounds. From a practical POV, that baggage area can handle lots more than 200#. However, as Eddie points out, weight vs load is something different. Weight (or more properly mass) is the stuff back there. The load, on the other hand, is the stuff x the load factor in a turn. In a 60 deg turn, that 200# back there is now a load of 400#. The floor of the baggage area is certified by Piper to handle that 400# without going to failure. Warm fuzzies required, because just about all the hardware for controlling the airplane including the battery cables, other than the fuel lines, are under that floor.

As long as the structure that had the seats installed on it, can handle the additional stuff, snugged down so it doesn't move, you'll be ok. But remember this is both a physics and materials problem.
 
I'm having a hard time thinking that removing the seats are a big deal. In my Archer, the seats come out very easily and are so light. I did not weigh them but guessing they could be 5 lbs each, if that. You can leave the seat belts in place to help wrap around your load. More importantly, load things in a way so they cannot shift in their moment during flight. If unsure at what location to use for locations not abeam your removed seats, assume a worst case aft location so as to be safe in the balance envelope. You can certainly weigh each removed seat to be more exacting of how much to subtract from the rear seat location, but really, if you ignored the weight and moment and use the weight and balance as if you retained the rear seats, your weight will actually be less and your CG will actually be more forward than calculated, which is all to the better.
 
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The C185 I flew for 30 years had easily removable (3-5 minutes, no tools) copilot, middle and rear seats. We hauled a lot stuff which would not fit without pulling some or all of them. Never thought of getting an a&p or faa rep involved....
 
And we routinely pulled the seats out of various workhorse Cessnas to haul such things as crayfish around the Bahamas.

To my recollection, the removal and implications was specifically covered in the POH, which is the key.
 
unsafervguy said:
With each airplane or rotorcraft that was not type certificated with an
Airplane or Rotorcraft Flight Manual and that has had no flight time prior to March 1, 1979
Click to expand...
So, that reg does not apply in this case?
 
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CC268 said:
Got a 1965 Cherokee 140 - my dad and I have discussed removing the rear bucket seat behind the pilot side as it will essentially never get used. We would leave the one that is behind the passenger seat. A few snaps in front and two fasteners in the rear removes the bucket seat I believe.

Would have to have a new W&B done. What about a 337 form?
Click to expand...

That is actually a really good idea. Those aircraft are more 2+2 types than true 4 place, the +2 being very small people at best. The one I flew used the area for storage.

The seat should be part of the equipment list, with its weight and moment shown. If not it will need to be calculated, which is not a big deal.

If I recall correctly, the base that the seat cushion bottom sits on is the shelf that covers the spar. That material has been certified to take 170 lbs over the area of the cushion up to 3.8 G. I think it would be fine holding a quart of oil and a flight bag! ;) The seat cushions might be more than 1 lb, which is negligible.

I loaded and unloaded many fuel drums from 185's and 206's. Along with heavy equipment parts, fish, moose meat, etc, etc. That is northern aviation. Was it 100% legal? Nope. Did we do our best? Yep. :cool:
 
It appears my local flora and fauna found out I posted on POA recently resulting in an ambush during my monthly coffee break at the octane club. At least I got free donuts for this post. Maybe a six-pack for the next one?? But I digress.

CC268:

It’s not so much the complexity of the task on your aircraft that dictates your direction but where it falls under Part 43: maintenance or preventative maintenance; and, who needs to sign the approval for return to service.

I’ll assume you’re a pilot owner so your only option is preventative maintenance under Part 43 App A(c). You’re close with (c)(15), but “replace” means remove + install not just remove. It’s splitting hairs but it is what it is. So that makes it maintenance (i.e., alteration) requiring an A&P.

But even if the seat removal was permitted in (c)(15) you would still need an A&P to amend the empty weight and empty weight center of gravity as this is only a maintenance function. The W&B calculations you do as a pilot are considered “loading” and are based on a certified empty weight/CG.

As to how much weight you can put in the removed seat area, this should be found in the POH/AFM/TCDS under a “max baggage/cargo” heading and usually lists a fuselage station number and weight limit.

While your mechanic would take it from here, I’ll include this part for your knowledge.

The next step would be to determine if this is a major or minor alteration. A quick look to 43 App A(a) finds removing a seat is not a major unless it is riveted to the spar, weighs 1000lbs or something similar. There is also FAA guidance showing the removal of items listed on an aircraft’s basic equipment list as minor alterations.

So no 337. Just a simple A&P logbook entry, equipment list revision, and empty weight and balance correction. To put the seat back in will require another write up and EL/W&B revisions.

Another tip, If you plan to remove/install this seat on a regular basis, you could make the W&B changes easier by using a running total type form like the “Owners W&B Form” found in most Mooney POHs, or like a Form C they use in 135/121 aircraft. This form provides a method to show multiple changes to the equipment list and W&B on one page.
 
Bell206 said:
It appears my local flora and fauna found out I posted on POA recently resulting in an ambush during my monthly coffee break at the octane club. At least I got free donuts for this post. Maybe a six-pack for the next one?? But I digress.

CC268:

It’s not so much the complexity of the task on your aircraft that dictates your direction but where it falls under Part 43: maintenance or preventative maintenance; and, who needs to sign the approval for return to service.

I’ll assume you’re a pilot owner so your only option is preventative maintenance under Part 43 App A(c). You’re close with (c)(15), but “replace” means remove + install not just remove. It’s splitting hairs but it is what it is. So that makes it maintenance (i.e., alteration) requiring an A&P.

But even if the seat removal was permitted in (c)(15) you would still need an A&P to amend the empty weight and empty weight center of gravity as this is only a maintenance function. The W&B calculations you do as a pilot are considered “loading” and are based on a certified empty weight/CG.

As to how much weight you can put in the removed seat area, this should be found in the POH/AFM/TCDS under a “max baggage/cargo” heading and usually lists a fuselage station number and weight limit.

While your mechanic would take it from here, I’ll include this part for your knowledge.

The next step would be to determine if this is a major or minor alteration. A quick look to 43 App A(a) finds removing a seat is not a major unless it is riveted to the spar, weighs 1000lbs or something similar. There is also FAA guidance showing the removal of items listed on an aircraft’s basic equipment list as minor alterations.

So no 337. Just a simple A&P logbook entry, equipment list revision, and empty weight and balance correction. To put the seat back in will require another write up and EL/W&B revisions.

Another tip, If you plan to remove/install this seat on a regular basis, you could make the W&B changes easier by using a running total type form like the “Owners W&B Form” found in most Mooney POHs, or like a Form C they use in 135/121 aircraft. This form provides a method to show multiple changes to the equipment list and W&B on one page.
Click to expand...

Sounds good to me!

I would definitely make the W&B addendum. Makes life easier down the road.
 
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My '69 Cherokee 140 has snap-out seat bottoms. But the backs are bolted to the plywood. The seat bottoms, might weigh as much as 2 pounds each.
 
bluerooster said:
My '69 Cherokee 140 has snap-out seat bottoms. But the backs are bolted to the plywood. The seat bottoms, might weigh as much as 2 pounds each.
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My seat bottoms and backs, together, weigh 16.5 lbs. I don't remove them so much for the weight, but instead for the room. Here is a pic of my Cherokee with the rear seats removed and those "panels" I described above in place. In this photo I left the seatbelts out to help secure our fold up bikes, but if I'm just putting soft luggage back there, I often put the panels over top of the seat belts, hiding them...

upload_2017-10-15_19-32-29.png
 
There you go. Get a mechanic to help and get an amended W&B. Just no anvils back there! :p
 
bluerooster said:
My '69 Cherokee 140 has snap-out seat bottoms. But the backs are bolted to the plywood. The seat bottoms, might weigh as much as 2 pounds each.
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Yep, same here. The cushions weigh about 2-3 pounds each, max. I can't imagine a requirement for a separate W/B. The error is in the noise.
 
paflyer said:
Yep, same here. The cushions weigh about 2-3 pounds each, max. I can't imagine a requirement for a separate W/B. The error is in the noise.
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pa:
I perfectly understand your point. Unfortunately, the Feds define negligible weight change as 1lb or less for aircraft with empty weight of less than 5000lbs, 2lbs for aircraft at 5000 to 50,000lbs, and 5lbs for over 50,000lbs empty weight.

The requirement for the separate empty weight change lies with its airworthiness certification. Most aircraft, even those operating under an experimental certificate, are required to provide a documented empty weight and empty weight CG at the time their respective airworthiness certificate is issued. TC’d aircraft also require an equipment list for certification.

Since the aircraft empty weight is part of certification, any alteration to it over the negligible limits above must be properly re-calculated per Part 43 and other FAA guidance by a qualified person in order for its airworthiness certificate to remain in effect. Experimental certified aircraft are exempt from this requirement as Part 43 is not applicable to them.
 
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