Pa28 seat adjustment.

There is a knob but it doesn't move. I don't want to break it off. I've read about blocolifts. Is that what I have?


  • If you have the adjustable seat, the knob/button is pushed rearward while the seat is unloaded. If the lift cylinder is good the seat will rise to its maximum height. If the seat doesn't move on its own, the lift cylinder has failed. If the cylinder is good you adjust the seat by applying the amount of weight to the seat to allow it to move to the desired height, then release the button. The seat will hold that position.
  • If the seat doesn't hold the position, is the cylinder likely bad?
  • Exactly, if the seat will not hold, the cylinder is bad.
    Here's the text of a previous post on this forum from Avlock.
    Our Av-Lok (PMA/FAA approved) is a direct replacement for the Piper (Blocolift)cyinder that is used to adjust the vertical motion of the crew seats. The Av-Lok is approved for PA-28, PA-32, and PA-34 models. Our Av-Lok sells for $250.00, as compared to the last known Piper price of $426.00. Since we received the PMA for our Av-Lok we have sold almost 50 units, including several to Piper Distributors. We have not had one return to date. The Av-Lok is available for immediate shipment.

    We also can overhaul the PL Porter hydrolok (SL10100) seat cylinders.

    If you would like to order or request additional information about this product or any of our other interior products, please do not hesitate to contact me.

    Chuck (660)885-8317 chuckatavfabdotcom

    Here's a direct link to the vendor. avlok I don't know the current price or if they're still offering the service, but you can check into it.
  • When I bought my Archer I did not adjust the seat height. One day for some reason I wanted to change the height to lower the seat. I depressed the handle and nothing. I tried a couple more times and the seat would not budge. Upon inspection I found that someone had placed a tube around the gas actuator and it was essentially a fixed position. Got the tube removed and the actuator was shot -- those puppies aren't cheap. Now seat works as designed.
  • My gas cylinder is shot and I am going to replace it with one from McFarland or AvLock. The seat will have to come out of the airplane for this replacement correct?
    Also, I would like to know if the lever for the seat back angle adjustment is supposed to be oriented towards the out side wall of the aircraft or in the middle where the fire extinguisher is located? Currently mine are to the outside and I am only able to get my fingers on the pilot side seat back lever. There is just not enough room left between the lever and the side cabin wall for the Co-Pilot seat back to be adjusted.

    Sincerely yours, for a safer G.A.
    Bristowe Pitts

  • Before replacing the cylinder, verify that the assembly is not missadjusted. The knob is supposed to pivot and that controls the valve on the strut assembly.

  • edited January 2022

    Bristowe, my seat back adjustments are on the centerline, not outboard. I suspect someone swapped your seats during an annual and no one has caught it.

    Seats are easy to remove.

    Eric Panning
    1981 Seneca III
    Hillsboro, OR (KHIO)

  • The pilot seat in my Cherokee has a gas cylinder that is missing the control button. I don't know how common this arrangement is. The gas cylinder had a tube fitting attached to the top and the seat has a bracket welded on the left side where a pushbutton is mounted. You push the button and that releases the gas cylinder. Or it did at one time. The tubing was filled with fluid and the button applied pressure hydraulically to the release pin on the gas cylinder. The fluid leaked out and it stopped working. I tried refilling the tube thingy, but it didn't last long. Apparently, there was a rubber diaphragm that rotted away. I removed the tube and found I could adjust the gas cylinder using my Swiss Army Knife screwdriver pressed on the pin. The tube has been off for years and I've lost track of where I put it.

    Now the airplane is in for annual and, for the first time ever, someone wrote it up. I never thought it was an airworthiness issue. Is there any way I can fix this?

    I doubt they really wanted to flag this as an airworthiness item, but I'm currently midway through redoing the upholstery and maybe they thought I could improve the project by fixing the seat. It's going to be coming apart soon anyway, as soon as I can get it out of the shop.

  • Search “Seat Hydro Springs” in the forum. I wrote a complete explanation of these things and all the nuances. Here’s a teaser pic to show you my solution.

    Greg Arserio | PP-ASEL-Instrument | N8390C 1976 Archer II | Rochester, NY (Based at KSDC)

  • Knots2u sells them and I think McFarlane does too.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • Am accustomed to flying Pipers with some age on them, so a question on what is operating normally versus what we might have accepted as normal.

    When pressing the button with the seat unloaded (example: simultaneously lifting your keester off of the seat), should the seat rise on its own, or will it still need some manual help to lift? Or does it depend on the actual mechanism?

  • Jacob:

    It should rise on its own. It does on my '78 -161.


  • As I recall, the lifts with the exposed springs can be rebuilt. The ones without springs have to be replaced.

  • My seat is missing the knob/ cable adjustment . I searched your paper on hydro locks but who has those parts? Also can the copilot seat be modified to fit the same set up? See pics-

  • Just saw the rest of your very detailed paper and will continue to search eBay or Texas salvage

  • During my reupholstering project, I discovered that the Hydrolock on the pilot seat of my PA28-151 had failed. I ended up contacting Aviation Fabricators ( They got back to me quickly, telling me that they would repair my Hydrolok unit for $334. (Hydrolok has a spring around it.) I mentioned the original hydraulic control had failed and the old part had gone missing. They told me they had a mechanical cable control they offer for $245. I went for the deal. Took a little over a week, aside from shipping. The Hydrolok looks and works like new and the mechanical cable fits and works exactly like the original, except that the cable is longer. I can hardly wait to finish my upholstery project to try it all out.

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