Pilots regularly make use of the expression “fly by the numbers”, and trust me, in flying there can be a ton of numbers. One group of fundamental numbers are the V-speeds. V-speeds are standard speeds that are important to get precision flight, and by precise flight I do not indicate some form of formation flying – I am talking about the sort of basic flying you actually undertake when you fly. They are rates of speed you should know, and in reality, my teacher requested that I know them before he’d let me solo.
There are numerous V rates of speed, not to mention that a lot more for many aeroplanes than you’ll find for others. As an example, there exists one rate referred to as VLE, that is actually the highest speed a person may fly with the landing equipment extended. That rate only pertains to airplanes with retractable landing equipment. I’ve have a fixed gear Cessna C-150L, consequently the plane doesn’t have a VLE.
The first V-speed is VR, or rotation speed. Rotation speed is the speed at which, when you’re rolling down the runway on take-off, you pull back on the yoke and leave the ground. The 150 rotates at 55 mph (and it gets there pretty fast – you apply full power, check the gauges and you’re pretty much there).
When you have taken off you will need to land, and that will require going slower as much as possible while nevertheless maintaing management in addition to flying. That introduces the 2nd V-speed – the stall speed (VS). Stalling will be when the plane no longer has sufficient lift to keep it flying.
There are at least two stall speeds – flaps up and flaps down. Flaps down provides more lift, hence a lower stall speed. In my 150 the VS is 48 mph, meaning that with full flaps it will fly as slow as 48 mph at a gross weight of 1600 pounds before it stalls. Although landing at a slow speed is easier on the airplane, you still need some airspeed to maintain control. I actually land closer to 65-70 mph airspeed.
The third V-speed is VS1, or clean stall speed. This is the stall speed at gross weight, but with flaps up. Flaps up is clean, flaps down is dirty. VS1 is 54 mph.
When you want to land you have to slow down (there’s an old saying “slow down to go down”). One way to do that is to reduce power, raise the nose of the airplane, and apply flaps. The amount that you apply can vary, but what you can’t do is apply flaps at too high a speed. Too much airspeed and you’ll damage the flaps. That brings us to the fourth V-speed, VFE, or maximum flap extended speed. On the airspeed indicator a white line begins below this speed, so its easy to see when you’re in safe flap range. VFE for my 150 is 100 mph.
VC is cruising speed, and that comes in at between 120 and 123 mph. The the maximum speed at which you can use abrupt control travel, or the design manouvering speed is called VA, and that’s a little bit lower, coming in at 109 mph.
Its important to understand that you can get a 150 going pretty fast, and pretty quickly. That can happen in a descent, especially a nose down descent. It’s not extremely dangerous if you keep your eye on it, but it is important to keep in mind. This speed, which the manufacturer advises that you never exceed, is called (of course), the VNE. Although I’ve said it can happen quickly I have to admit I’ve never gotten close, because the VNE in the Cessna C-150 is 164 mph. However, speed does climb pretty quickly in a nose down attitude, so, as I said, its something to remember and keep an eye on.
Two V-speeds come up in relation to climbing. Normal climbs are performed at bewteen 75 and 85 mph with no flaps. This is best for cooling the engine (or more to the point, keeping it cool). We could say that the best rate of climb, VY, comes in at 77 mph.
There is another way to think about it as well. VY is the fastest climb rate in terms of time. In other words, at VY you’ll rise more feet per minute than you will at the second V-speed for climbing, VX, or best angle of climb. Best angle of climb is a measurement of how much you climb in relation to how far you travel across the ground. Its slower, about 69 mph, so you climb slower, but you don’t have to travel as far across the ground to get there. Obviously its helpful to know this speed if you’re concernedabout clearing obstacles at the end of the runway.
Its interesting to note that VY decreases with altitude gain, while VX increase with altitude gain, becoming equal at the aircraft’s service cieling, wuhich in the C-150 is 13,000.
The last of the basic V-speeds is VBG, or best glide speed. This is important in the unlikely event that you experience an engine failure, or the likely event that an instructor throws a simulated power failure at you. You have to put the aircraft into the best power off glide speed, which is the speed that will allow the plane to glide the longest amount of distance, so that you can find an airstrip, make it back to the mainland or find somewhere acceptable to put the plane down.
If you want to read more about flying go to www.bushpilotintraining.com, or google Italo May. You can find out lots of stuff, and do the Online PSTAR quiz.