Time to abandon the project?

N34TMThis past weekend I was able to view a Fisher R-80 in person for the first time.  It’s a nice looking airplane and everything seemed to be falling into place.  Then came an in-depth conversation with the builder/pilot.  The following concerns came to light:

  • Build time was significantly longer than advertised, roughly 2,400 hours as opposed to 700.  That’s twice what I was hoping for.
  • Stall speed seems to be in the 45-50 mph range.  That’s 10-15 mph higher than advertised.
  • Cruise speed (75% power on a Jabiru 3300 motor) is about 70-75 mph, about 10 mph less than advertised.
  • The aircraft flies with a pronounced nose-high attitude, and level flight could not be maintained without using maximum elevator trim.

Each one of these points in its own is a concern.  Each could be enough to dissuade me from building an R-80.  Before making any decisions I wanted to hear from other builders and pilots, to find out if these are common faults with the type.  I scrounged the internet for the contact information of as many R-80 builders and owners as I could find.  In the end I found 10 email addresses, and sent each one a very brief survey.  A couple of the emails bounced, a few more have not yet been answered, but I’ve gotten 5 responses.  They all tally with what the local builder found.

  • Build times range from 2400 to 7000 hours
  • Stall speeds range from 45 to 55 mph
  • The nose-high attitude is a universal trait, at least when built to plan.  Some builders opted for a higher angle of incidence of the wing, I’ve not yet heard back from any of them to find if it made a difference.
  • Empty weights came in about 150-200 lbs higher than advertised, in some cases leaving as little as 180 lbs of useful load for pilot, passenger and baggage.
  • Stall behavior is to “mush” at a descent rate of over 1,000 fpm.  The aircraft does not drop its nose nor self-recover from the stall.  A close watch must be kept on the VSI at low altitudes.

All of this is bad news for this 80% scale Tiger Moth.  I haven’t made a firm decision yet, but I’m certainly entertaining all options at this point.  I would like to see if the problems can be overcome aerodynamically… that’s one of the great things about building an experimental plane, you are under no obligation to follow the plans.  But, it’s always possible that it cannot, or that it would take too much work, or that the improvement can’t be assured without building the plane anyway.  If that’s the case, I’m afraid I’ll have to walk away from this project altogether.

One response to “Time to abandon the project?

  1. Dave Hertner, President of Fisher Flying Products, contacted me with the request that I include, as a counterpoint, comments provided by Ivan Campbell regarding his experiences building 4 Fisher R-80 aircraft. An utterly reasonable request, you will find Dave’s full email below.

    Thanks,
    -Liz

    —————————————————————–

    Hello,
    I would like to provide a counter point to your article posted on Feb 25, 2016.
    Here is a response from Ivan Campbell of Campbell AeroClassics to comment on your post. Ian has built 4 of our R-80 Tiger Moths and is the foremost authority on its construction and flight characteristics.
    I would appreciate it if you would post his reply as a comment to your post. I have received a number of queries regarding the post content.
    Thanks,
    Dave Hertner
    President of Fisher Flying Products

    “Hi Dave
    In response to the article:
    All I can say is we have built 4 here some years ago and all four flew well with no noticeable issues. We worked out c o g and adjusted our engine mounts lengths to accommodate our Suzuki 1300 twin cam motors with Raven Redrive and they flew straight and level. One was fitted with a 912 s but obviously the cowls were not as original as the nose bowl and cowls that I made.
    All manufacturers tend to understate build time but claim that is the basic assembly. As you know we all want to personalize and refine the appearance if we have pride in our work. We never worried about the time we took as we enjoyed the build process and found the kit to be generally very good. We did modify some areas which we passed on to your predecessor. I will explain later

    The aircraft is so benign in its stall in fact it just mushes and descends at a controllable rate. There is no tendency to drop a wing or spin like the original. We never altered wing configuration from standard plan set up and it flys beautifully. It is lazy in a loop and has slow response to aileron rolls. It is not an aerobatic wiz ship but a lovely classic cruiser which I have shared with hundreds of people over the years. The Suzuki 110 HP cruises at 75 knots easily and straight and level will do 90 kts. It is a draggy aircraft and has a steep decent with no power and speed is stable for a landing. (my Spitfire descends at 1500 FPM power off so the tiger is no problem.)
    The Tiger does need at least a good 100 HP to perform well in climb. Some have tried less with poor results.

    The mods we did from memory are;
    Ply wood sheets down the entire fuse sides
    Cut the foot locker centre back to the straight firewall leaving each side for the front rudder peddles. This allowed our heavier Suzuki to be moved rearward for balance.
    Made right angle metal brackets that the engine mounts bolts onto and brought them back along the longerons sides on the outside of the ply.
    We double plated the aileron bell cranks and pivot fixtures to stop over hung bolt movement
    Placed our battery in a slide-able mount behind pilot seat so we could adjust any fine weight distribution for flight trim and pilot weight. We use neutral trim normally and slight adjust only with fuel and passenger variations
    We also lifted the front of the horizontal stabilizer to the maximum. This lifts the tail and also probably why they fly nose high. It also helps in the flare for landing. These things are all normal considerations for setting up an aircraft but maybe some builders need to be informed. (It might be a good thing for you to make adjustable brackets for the front stab fix point and even increase the gap to allow for more rise at the front).
    It sounds like some builders have not got it right and are not getting the aircraft up on the step hence slower speeds.
    We replaced the main aluminum undercarriage struts drag link and suspension with 4130 as they can bend in a heavy landing
    That’s about all I can remember. I have been flying my R80 for about 14 years along with my Titan Mustang and Supermarine Spitfire MK 26 B with 420 HP V8 Corvette, but I still love flying the Tiger.
    Having built the Tigers, 6 T51 mustangs, 3 Spitfires, my own design weight shift trike, I am starting to learn a bit about design, kits, setting them up and flying them.
    Hope this helps

    Cheers Ivan”

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