Canair 506 Transition Training

June 14-16, 2004

 I was looking for an excuse to spend some time with my 12 year old son so it seemed like a good idea to go hovering.  In fact, it generally always seems like a good idea to go hovering….  But this was a special case as I decided to get transition training on the Canair 506 hovercraft.  This craft is 20’ long and weighs a ton (literally) which is substantially longer and heavier than the hovercraft I had flown before. 

 I had taken my newly received 506 out on Lake Somerville for one of the Houston hover-ins in May.  Even recognizing that the craft controls were not functioning properly when I had it out, it was clear to me that this craft flew like no other craft I had ever been in before much less flown.  As a matter of safety and to learn more about the craft, I called Larry Threlkeld at Strike Zone Charters Inc in Big Pine Key, Florida.  Larry is an interesting guy.  He owns Strike Zone Charters in Big Pine Key that provides offshore fishing, scuba, snorkeling and like diversions for the many folks vacationing in the Keys.  But Larry also owns a Canair 506, used to own the 506 (actually a 504L) I now own, and had the opportunity to visit the Canair factory and talk to Ron Fishlock the designer of the Canair line of hovercrafts.

 Larry purchased both my craft and his current craft from Les Adkins of Canhover the successor to Canair.  Canair had gone out of business in August of 2000 and Canhover purchased the assets.  During his trip to Canada to see the factory, Larry was able to take pictures of the one and only Canair 509 being assembled and the first Canair 512 being produced.  Both the 509 and 512 craft have duel engines and fans.  He also procured a copy of the Canair promotional VHS tape which he kindly loaned to me.  The tape features the prototype Canair 504L doing the things a hovercraft can do.  It goes on water, land, snow and ice.  But, it also contains raw footage of the first 512 on what looks like its first flight trials.  The off-hand verbal comments by an unseen commentator at the end when the 512 is brought off cushion are hard to hear but interesting.  Rob Tilton has graciously offered to convert it to a digital format for me and I will try to post the tape on my web site in due course.  I also learned that the first four six seat crafts were referred to as 504Ls.  The 504 was the designation for the 4 seat version and the “L” stood for the “long” six seat extended version.  For serial number 5 the designation was changed to 506.

 It was interesting to see the 506 prototype and note the changes between it and my craft which is serial number 3.  One change I noticed immediately is that the window wiper was mounted on top of the front window where as in my craft and all the other crafts I have seen it is mounted on the bottom.  This change is more than just a passing curiosity as I have spent many hours now restoring the window wiper mechanism on my 506.  It was totally and absolutely corroded.  None of the shafts would turn even with substantial leverage being used and the motor was pretty much a basket case.  You can see the pictures on my web site.

 The reason for the extent of the corrosion is that the mechanism is mounted in a compartment that is exposed to cushion air that is provided for the heater radiator.  This air will have salt mist and the like when the craft is operated in salt water such as in Florida.  Even if the metal is treated, over time the treatment wears off and corrosion sets in.  By mounting the mechanism inside the craft and at the top of the windshield, this problem would be very much reduced if not eliminated totally.  I asked Les Adkins about the change and he said the original design was an eye sore and it cost more to route the wires and window cleaning solution up there.  Well, I am not sure that was a good trade off but that is why the change was made.

 Of course, the original mechanism is no longer available so it was either make new holes in the front of the craft and fill in the old holes, or spend the time to restore the old mechanism.  I did not want to make holes in the craft so I was stuck restoring the mess.  As a side note, the bearings used in roller blade skates fit the frozen bearing in the motor.  So for the cost of a trip to the local sports store and $24 I became the proud owner of the best 16 new bearings (only needed one) they had to offer.

 I was also interested to see all the changes from my craft to the one Larry owns which is serial number 7.  His was the next to last of the 506s built.  Most of the changes were small but some were major.  For example, his control stick was made much shorter than the prior ones used in earlier crafts as the longer stick tends to hit the control panel and, for guys, if you have to quickly pull the stick back to go into full reverse, you will plan better next time….  Many of the switches on my center control panel had been moved to an overhead control panel in Larry’s craft.  This change was made for ease of use and reliability as the center control panel moves forward and backwards with the front seat.  So there is more opportunity for wires to chafe and cause opportunities with the prior design.  The front seat moves forward and backwards powered by an electric motor.  This is how the craft is trimmed fore and aft.  There were other minor changes but his craft also had a larger engine of 125 HP where as mine is 100 HP.  However, the engines are only used at about 5000 rpm so the HP is really about 75-80 HP and even that is normally only done when you are getting over hump.

 So how does it fly?  Well, in short, like a long and heavy craft.  To put this in perspective, my AC-3 was about 10’ long, weighed 650 lbs, and had about 70 HP.  The Scat II I had before that weighed maybe 100 lbs less and had 64 HP (I put on a Rotax 532).  The Canair 506 is twice as long and at least three times as heavy as either the Scat or AC-3 and has about the same HP.  Weight and size make a difference in how a craft performs for the same HP.  One of the biggest differences is getting over hump speed on water.  The 506 performs best on shallow water or water that is deeper than 14’.  If the depth of the water is in the middle, it is a long slow slog to get over hump speed.

 The other major difference is that you have to plan quite far ahead before you approach land to do what you want.  If you are going to set down it is no problem as you just head on up to the land and then go into reverse to slow the craft and set down where you want.  The reverse is a nice feature and allows you to hover in position or even move sideways with little if any forward motion.

 However, if you want to parallel the land, then you need to start the turn pretty early as the craft is heavy and has considerable momentum.  You cannot just turn the rudders sharply and gun the throttle like on an AC-3.  If you do, the craft will just flip head to tail on you and now you are heading toward the shore tail first and thinking that sure was a stupid thing to do.  To make the turn you have to move the control stick in the direction you want to go and then center it to keep the back from coming around on you.  If you are over aggressive, then the tail will turn too much and you have to move the control stick the opposite way to straighten up the craft before you continue the turn.  Gunning the throttle makes it harder to move the rudders and adds lift to the back which makes it even more likely to flip around on you.  You are better off actually having the tail drag a little in the turn.  Generally however, the throttle is set at a particular RPM of around 4200- 4400 RPM and just left alone.  The speed is controlled by the how far forward or back the stick is moved.  At a mid position of the stick, the rudders are partially closed which reduces the thrust while not changing the lift.

 The seat trim switch is used often with getting over hump speed, when slowing down or to compensate for the effects of the wind.  To get over hump speed, the seat is moved all the way forward and you are almost against the windshield.  The throttle is moved to full and the lift/thrust control in moved to full lift.  The stick is moved into full reverse for about 6 seconds to clear the skirts of water and then the stick is moved full forward to give maximum thrust.  As the craft picks up a little speed, the lift/thrust control is moved to a mid position to give more thrust.  As the craft passes through hump speed, the throttle is reduced at the same time the seat is moved backwards to trim out the craft.  It is kind of a one arm paper hanging affair until the craft is over hump speed and then it is just a matter to trim the craft for the conditions.  If you have a head wind, then the seat is moved somewhat forward and with a tail wind the seat is moved more rearward.  The RPMs are pretty much just set and left at the desired range for the speed you want to go.  The craft will go about 30-35 mph with no wind over water.  The faster you go the more you move the lift/thrust control to add more lift.  If you did not mind the noise, you could just set the throttle at full and control the speed from maximum to zero with the control stick but the rudders would be harder to move with full thrust.

 I asked my son which hovercraft he preferred to ride in given a choice between the AC-3 and the Canair 506.  He chose the 506.  The 506 is a much smoother and far more comfortable craft to ride in than either the AC-3 or the Scat.  I operated the 506 for many hours going around the tiny islands in the Keys and practicing getting into and out of pretty narrow areas.  I only felt like we would plough in once but I just added more lift and moved the seat back to keep it from going in.  There was a lot of warning and it recovers smoothly.  The cause was pilot error (mine) and after my first hour of practice it never happened again whether we went into a head wind or we had a tail wind. The 506 is a craft that demands your attention but it has unique abilities few others have.

 After flying Larry’s craft and my craft a little now, I would say the only major change I would make is to add more HP to give it enough thrust to get over hump speed in mid depth waters faster.  I would guess it would take about twice the HP that the craft now has to do that.  This is a modification I will consider in more detail this winter.  However, higher thrust will mean that the rudders will be harder to move.  On the 509 and 512 crafts, the rudders are fly-by-wire using electric controls and servos.  The electric system eliminates the operator fatigue issue if the operator has to fight the engine thrust often such as close quarters maneuvering.  I also may consider moving the seat control from the center panel to a position by the throttle level like on Larry’s craft.  The center panel position is pretty inconvenient when you need to move it a lot.

 My son and I had a great time in Big Pine Key and highly recommend Strike Zone Charters for seeing the reefs and fish if you like scuba or snorkeling.  Larry may even agree to give you lessons in his 506 but you will need to arrange that before you go!  Now I can’t wait to put my wiper mechanism back in the craft and go hovering.  Lane Crampton called and wants to go to the lake this weekend.  Well, it seems like a good time to go hovering….