Prop Strike!
Our aircraft G-ZTED is a Europa Classic Monowheel Rotax 912S with an Airmaster
A332 Propeller.
Our lovely Europa, our pride and joy, was only 17 hours old when we went to our
first fly-in. I was taxiing on rough grass and slightly out of wind, the tail
lifted and, o woe and thrice woe, the propeller dug into the soft turf breaking
three blades off and damaging the variable pitch mechanism of the prop.
Lots of thought and soul searching not to mention upset later we have come up
with
a set of rules for taxiing our Classic Monowheel which will hopefully avoid
this happening again. The Rules are on the back door of our trailer stuck to
the broken blades to remind us. I would like to have seen these and thought
about
them before it happened to me. I offer the story here in spite of the
embarrassment,
knowing that if it saves just one propeller that it is worthwhile.
The elevator of the Europa is powerful, it's brakes are good and the Centre of
Gravity is not that far behind the mainwheel. Coupled with this we have the
Rotax
912S with an Airmaster A332 constant speed prop which, when set to fine,
can produce a thrust of over 500 lbs on the ground. Each one of these things can
lead to the tail becoming light and in a number of circumstances they can add
together to cause a certain propeller strike. All these forces act in the same
way conspiring to wreck your propeller, your day, your self esteem and your
bank balance.
So, to counter this, we have devised a set of Rules which I am going to adhere
to.
It should be food for thought for new Monowheel owners.
Rule 1: DO NOT Use more than 3000 rpm to taxi.
This puts a limit on the amount of thrust which tends to tip the nose forward.
If the ground is so rough that more than 3000 rpm is required then you should
not be there. Shut Down and pull her out. It is a lot cheaper than a propeller.
Rule 2: DO NOT Taxi with Power against the Brakes
This is much the same as number one. Taxiing against the brakes produces a
tendency
to tip the nose forward. I can think of no occasion when it is a sensible
thing to do so it is now off limits.
Rule 3: ALWAYS Do the run up check directly into wind
This may seem obvious but given the situation where you were say 40 degrees out
of wind in a blustery 25kt wind. The power goes on for the run up against the
brakes. This makes the tail lighter but you pull the stick right back. Due to
the strong side wind the prop wash is not operating on the upwind side of the
elevator and the aircraft is very tail light. The blustery wind gusts under the
windward elevator and the equation is suddenly not in your favour. Obey rule
three and this won't happen.
Rule 4: ALWAYS Centralise Control Stick when taxiing out of wind
Again this is obvious. The all flying elevator is so powerful that if pulled
back
it is enough to lift the tail all on it's own without any of the other factors
helping it. Due to the taxiing attitude of the monowheel the ailerons are
best centralised out of wind.
Centralised controls make the Europa Monowheel quite stable when taxiing
downwind.
Rule 5: NEVER Taxi on Rough Grass
This is a bit extreme but after our experience we are going to stick to this.
The
Europa Monwheel's big wheel makes landing on rough fields possible but taxiing
on rough grass is risky. If 3000 rpm won't take you then Shut Down and get
out and pull it out. Believe me it is cheaper to do that.
Rule 6: NEVER Use Power to overcome obstacles. When you get stuck. SHUT
ENGINE
DOWN and get out and pull it out.
OK this is Rule five again but it is the most dodgy thing to do. Directly into
wind it may be possible to get away with more thrust but our Airmaster Propeller
is a wonderful piece of kit and makes our aeroplane very good cruising machine.
It can pull the nose over with very little help. Why risk it.
The above instructions are now incorporated into our Pilot Notes.
We are just getting to know what a fantastic aeroplane we have made.
See you around.
Justin Kennedy
G-ZTED
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