A FEW THOUGHTS ABOUT FLYING FROM GRASS DURING THE WINTER
The winter season is noted for being, wet and windy! Then, along comes that rare blue day. The aviator sticks his nose out into the fresh air and immediately thinks of flying. Muscle memory kicks in and he can feel the control movements and the response of the plane ….. It’s still miles away tucked up in its hangar but he might as well be strapped into the cockpit. It’s not a question of whether to go flying but just how soon!
Arriving at the airstrip, it’s time to put a lid on that flying impulse and get into responsible aviator mode.
Is the strip in a suitable condition for safe flying?
There is no alternative to slipping on the wellies and walking the taxiway and runway. Imagine opening up the throttle for take-off. How will the plane accelerate? Imagine the landing. Is there any grip for steerage and braking?
First sign of a problem is the squelching of the wellies. Soft ground allows the tyres to sink in and the spats (take them off for the winter!) to fill with mud and both will reduce acceleration. A good technique is to dig the heal in as though you were setting up a rugby ball for a place kick. If it jars the leg, it’s probably ok. If it splatters your trousers with mud …… well it’s time for coffee in the club house.
The length of the grass and how wet it is, also affects acceleration. At the beginning of the winter season, temperatures start to fall and grass growth stops. There comes a point after which the grass is too wet and the ground too soft for effective grass cutting. Timing of the ‘last cut’ is crucial. Anything much more than a hands width high, is going to slow acceleration. Add to that the amount of moisture and it is very possible that your plane will never reach to lift off speed and at best will use up far more runway than usual to achieve it. Often on a winters morning the dew on the grass makes flying unsafe. Blue skies and a few hours drying and it’s possible in the early afternoon. Choose your time.
Of course it’s not just about the take-off. Many modern microlights have an astonishing power to weight ratio and in any headwind are off the ground in as little as 50m! However, what goes up, must come down at some point. Landing is another matter. The plane may not be exactly lined up with the centre line requiring some directional control during the ground roll. Is there any grip on the grass surface? Will you be able to control direction or is there a risk of going off the runway? Don’t forget that the runway surface is likely to have soft patches. Catching a wheel in a soft patch will induce a swing. Will you have sufficient grip to correct it?
The use of brakes should be avoided on grass but none the less many aircraft depend on them for differential braking and steering. Is there sufficient grip for braking? This is easily determined while walking the strip. If you find yourself waving your arms around to keep your balance, it’s probably a sign from the flying gods …… leave it in the hangar. Many private strips have both a longitudinal slope and a transverse slope. The former may require braking to slow down and the latter to maintain the centreline. These strips require better conditions than level strips.
Now, earlier I mentioned retiring to the clubhouse for coffee. It’s actually not such a bad idea even if the taxiway and runway appear to be good to go. The other major factor is the wind and the best way to make an assessment is to watch the windsock and or anemometer for 20 mins or so. So put on the kettle! A headwind makes a significant difference to the ground roll and can offset slightly soft/damp ground. No wind may be inviting but will likely result in a longer take-off and landing run. A crosswind is likely to be a no go even if well within your personal abilities in normal conditions. Limited directional control may result in an excursion off the runway.
While it’s always best to make your decision before getting the plane out of its hangar, getting it out should not automatically mean that you are going to fly! While taxing, does it require more power than usual? Are you having difficulty steering?
ON THE RUNWAY:
CARBURETTOR ICING. Taxying over wet grass is conducive to carb ice and it is not recommended to taxi with the carb heat on as the air is unfiltered in many aircraft types. However, when lined up with checks complete and ready to go, do one last action! Run the engine up so that there is a decent exhaust gas temperature (at least the mag check rpm) and apply the carb heat for a full 15 seconds. One crocodile … two crocodiles … three crocodiles etc. Clear any carb ice before attempting to take off.
GO OR NO GO. Despite your best efforts walking the runway etc. it’s still vital to stay awake during the take-off run. Is the engine achieving full power? Can you keep the plane straight? Is acceleration normal or if impaired, is it sufficient to get airborne safely? At what point down the runway must you abandon the take off in order to have sufficient distance to stop?
Plenty to think about. On those occasions when it’s a go, enjoy the flying because opportunities during the winter may be few and far between. Maintaining currency is also valuable.
Enjoy the flight and don’t forget to clean the mud off afterwards.