After takeoff, it is best to stay above the runway and not drift to one side. Many students have trouble with this and the skill builds with experience. Continue reading “How to stay over the runway after takeoff”
I enjoy simulating emergencies for students. One of my favorites has to do with the oil pressure.
As the student lines up the plane for takeoff I watch their eyes. When I’m sure they are looking out the window I say, “Woah … the oil pressure just spiked!” Most people look down at the gauge and see the pressure sitting in the green. Continue reading “Abnormal Oil Pressure”
Retractable gear planes fly faster and save fuel because they have less drag. The downside is that there is a risk of landing with the wheels retracted and causing significant damage to the plane. For this reason, some planes have been equipped with an automatic landing gear extension system.
Flaps are very useful for giving an airplane good handling characteristics at low speed. They are vitally important for giving fast planes the ability to go slow for takeoff and landing.
There are 6 types of flaps
- Plain Flaps
- Split Flaps
- Slotted Flaps
- Fowler Flaps
A simple hinge at the rear of the wing is used to make plain flaps. They are easy to design but they can’t provide much lift before the drag increases very significantly.
Since increasing drag is one of the purposes of a flap the performance is not too bad for landing. When taking off though, drag is not desired.
The reason this flap has so much drag is because the air from above the wing tends to separate and become turbulent when it has to flow downwards at such a steep angle. Think of it like a car on the highway having to make a sharp turn to stay on the road. This airflow separation is like that car spinning out because it can’t make the turn.
Turbulent airflow separation above the wing reduces lift.
The split flap surface is actually below the wing and pushes down out of the bottom. It does provide some lift but it creates a lot of drag and is almost like a speed brake under the wing.
This is the most common type of flap because it is relatively simple to design and build but provides a huge benefit over the plain flap. The slot created when the flap extends allows air to flow from under the wing.
This airflow provides a cushion for the air from on top of the wing to keep it from separating. It also flows along the top of the flap surface. These two benefits combine to create a lot of extra lift.
Fowler flaps are complex but provide a lot of benefit. They act like slotted flaps opening up a channel for air, but they also slide outwards as depicted below. By sliding out from the wing they greatly increase wing area.
Put simply, they make the wing bigger. A bigger wing means lots of lift!
Most modern airliners use double or triple slotted fowler flaps. These have several flap surfaces that extend out from each other as the flaps are lowered creating a much larger wing with several slots for air to pass through.
This modification to the leading edge of the wing provides a channel of air that is pushed up over the wing and channeled towards the upper surface. At low speeds, this simple fixed device can increase the critical angle of attack (the angle at which the wing stalls). This means that the plane can fly much slower without stalling.
Slats are another type of leading edge flap. They slide down at low speeds and provide a large increase in lift like the fixed slot. The benefit of the slat is that it is retractable and won’t create extra drag at high speeds because it slides up into the wing surface.
We commonly think about how the wind pushes the airplane, but did you know that the wind pulls as well?
Cruising with a tailwind pushes us forward while headwind pushes us back. If we are flying with a crab angle we can look at the ground and get the feeling that we are flying sideways. In these cases, the wind is pushing us from whichever direction it is coming from.
Sometimes the wind pulls us
This problem has been around for a long time!
Imagine a 747 is sitting on a conveyor belt, as wide and long as a runway. The conveyor belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?
The correct answer is Continue reading “The Airplane Conveyor Problem”
Departing from a short field is an important skill for any pilot. There is a standard procedure to follow and plenty of factors to consider.
The procedure to depart from a short field can be found in the Pilot’s Operating Handbook for the aircraft. However, it will go something like the following for most light aircraft. Continue reading “Short Field Takeoff”
No airport is officially declared to be a short field because a field that might be short for a 747 could be very long for a Piper Cub. Every airplane is different. Continue reading “What is a short field?”
You might think that departing from the pattern at a non-towered airport is simple, and it usually is. However, there is a standard way to do it that is safer than the alternatives.
See this diagram from the Aeronautical Information Manual.
For our purposes, we are only interested in #6. Notice the only two ways out of the pattern are straight ahead, or a 45 degree turn to the left. This is what the AIM says about it:
From AIM 4-3-3 If departing the traffic pattern, continue straight out, or exit with a 45 degree turn (to the left when in a left−hand traffic pattern; to the right when in a right−hand traffic pattern) beyond the departure end of the runway, after reaching pattern altitude.
It’s pretty clear from this that there is only one real way out of the pattern.
When can you turn?
The AIM recommends a straight out departure, but you will need to turn at some point unless you happen to be going where the runway points.
Continue on your straight out or 45 degree departure until you are outside of the normal traffic pattern (2 miles from the airport).
Make a plan that helps you to maintain clearance from the traffic pattern if you need to pass back over the airport. This means being at least 500 feet above pattern altitude before passing over any part of the pattern, including the inbound 45 degree leg.
Why not depart from downwind?
Have you ever heard the story of the high wing airplane flying just under the low wing airplane, and neither can see the other. This kind of thing can really happen, and downwind is where it would occur. If you are climbing through the pattern while others are maintaining altitude in the pattern you are inviting this type of setup.
Conversely, it is hard to imagine this occurring on a straight out departure leg. Keeping traffic separated based on activity makes the pattern safer by making it easier to anticipate where planes are and what they are doing.
Most pilots know that way back in 2010 the FAA retired the phrase “Position and Hold”. Instead “Line Up and Wait” came into usage, indicated to an aircraft at a towered field that they are to taxi onto the runway, line up for departure, and then wait until takeoff clearance is given. Continue reading “Line Up and Wait”