The Two Fundamental Concepts that Greatly Simplify NDB Approaches

It was an instrument lesson and an actual approach. We were flying a Piper Arrow into the Monterey Peninsula Airport just north of the famous Pebble Beach Country Club. The localizer was out of service. The only available approach was the NDB  (non-directional beacon) approach using the outer compass locater nestled up against  the outer marker on the breakwater where the peninsula met the Pacific. Flying the  Monterey Bay coast is one of the most beautiful sights in aviation. Above the cloud 

layer the sky is dazzling. Green and brown hills push up through the seemingly  perpetual low stratus more than a thousand feet above the cloud tops. On that day, the  tops were less than 1,000 MSL. 

One fundamental principle of NDB approaches is to fly the course that takes you from  the radio beacon to the missed approach point. The other fundamental principle is that  the accuracy is limited by the accuracy of your gyrocompass. Any drift or 

uncompensated deviation degrades your ability to fly an accurate course. 

The NDB approach requires that you use your gyrocompass for heading reference and  your radio compass (automatic direction finder, a.k.a. ADF) for orientation. The fatal mistake is to simply follow the needle. The seductive part of an NDB approach is that 

half of the time, following the needle works just fine. That half is until you pass over  the beacon. Once your needle points back at 180°, all the radio compass tells you is  that your tail is pointing at the radio beacon. You could be flying in any direction. 

I decided to let Ralph try the approach and told Approach Control that we would execute a missed approach at or before the missed approach point (MAP). Ralph and I  had talked about NDB approaches. I was not sure he understood them. Here was a 

place where a mistake could be fatal. So during our procedure turn outbound and still  above the clouds, I told him to be prepared for me to take over and execute the missed  approach. 

We descended into the clouds. Shortly after passing the NDB, we were 30° degrees  off course and headed into high terrain. I asked Ralph what heading would get us to  the airport. He could not tell me and said we were doing just fine. He started to argue 

with me about flying a missed approach and who should be flying. I applied full  power, retracted flaps and gear, and told ATC that we were missed. Ralph decided I  was serious and capitulated. Once we were on top Ralph stared at the mountains and 

turned pale. © Copyright 2008-2010 Douglas W. Daniel. All rights reserved. 

Assume the course from the NDB to the missed approach point is 100°. Make it easy by assuming that the inbound course to the NDB is also 100°. Fly a 30° intercept to the inbound course. This would be either 70° or 130° depending on the approach procedure. If it is 130°, your heading is 30° to the right of the inbound course. Your ADF would read 30° to the left of straight ahead or 330° when you intercept the course that you want to follow. If you are two miles or more from the NDB, start the 

turn inbound just a few degrees early so you can roll to wings level just as the ADF centers. Initially fly the magnetic heading shown on the approach procedure. In a few moments the ADF will start to move to either the right or left. It always does.

To interrupt the narrative, how do you know when you are on the path that takes you over the NDB to the airport? The answer is when the ADF needle is off to one side and the gyrocompass if off by an equal angle to the other side. Earlier your 

gyrocompass was off by 30° to the right and your ADF was off by 30° to the left so you were on the course but not on the proper heading. We'll try to nail this down next. 

Continuing to track inbound to the NDB, fly trial headings and watch the ADF. Your first try is the heading on the chart. If the wind blows you to one side, turn back far enough that the ADF is pointing to the other side. Suppose the wind blows you to the 

left until the ADF points to 005°, turn right until it points to -005° which is really 355°. This would require a 10° turn changing your heading from 100° to 110°. Hold that course until the ADF moves left to -010° or 350°. If the ADF moves right, then 

you did not turn far enough, but let's say you did. Once again the radio compass is off an equal but opposite angle from the gyrocompass. You are on course but not on the proper heading. You know that the correction angle is between zero and ten degrees because zero was taking you to the left of the inbound course and ten would have taken you to the right of it if you had continued. If the wind compensating angle is between zero and ten degrees, then the heading to fly is between 100° and 110°.You 

may as well try half way between. That would be 105°. It won't work either exactly, so keep refining your heading. 

This is the procedure that you follow all the way to the missed approach point. Once past the NDB your corrections are left or right of straight back rather than straight ahead. 

To put it in a nutshell, for an NDB approach or any other kind of approach, fly headings, don't chase needles.

Private Pilot Training Online focuses on the little things that hold pilots back; dispels the myths that make learning and flying unnecessarily difficult; and makes the ‘hard’ subjects easy.

Douglas Daniel, long time flight instructor, invites you to visit athttp://PrivatePilotTrainingOnline.org for more flying articles like this one. You may also feel free to contact Doug by visiting his website.

 

Three Steps to Perfect Landings

There are just three fundamental skills you need to know to land an airplane safely and consistently. They are airspeed control, projected glide control, and controlled slow flight. You can learn each separately. But you use them all to land safely and
consistently.

The most fundamental and easiest to learn is airspeed control. You should start with it. Then you should master slow Dutch roll thoroughly at various airspeeds, aircraft configurations and angles of bank. Concurrently you can learn to control the projected
glide point while maintaining a constant airspeed. Airspeed control and projected glide control bring the pilot to the right place at the right airspeed to start the transition from the approach glide to the landing phase.

Control airspeed with the elevator; fine-tune airspeed with power, flaps and landing gear. Monitor airspeed with the airspeed indicator, and then adjust your pitch attitude with the elevator to change your airspeed. If you add to the airplane's drag, you will
be forced to pitch down to maintain constant airspeed. The opposite is true, as well. If you add power, you must lift your nose some, and so forth. Once you have learned to control your airspeed in various flap, landing gear, and power settings you are ready to move on to controlling either your projected glide point (PGP) or mastering slow Dutch rolls (SDR).

Controlling your PGP is only slightly more difficult than controlling airspeed. During a constant airspeed approach, you will see a point on the ground that is staying absolutely still in your field of view. This is where you would go if nothing changed and you continued your downward glide. This is your PGP. If you keep your airspeed steady, your PGP will move farther away from you when you add power and it will come closer to you when you reduce the engine's power setting. More drag brings PGP closer; less drag pushes it away. There is really not much to controlling PGP, but when a pilot runs off the far end of the runway almost certainly poor PGP control, poor airspeed control, or both was the problem. You have to control them both to arrive at the right place and the right airspeed to execute a good landing.

Ironically, once you have flown the proper approach, you no longer need to control either airspeed or PGP. A new set of skills is required to execute the landing itself. Fortunately you can learn most of these skills with one exercise conducted at a nice
comfortable attitude. You learn it by doing SDR in slow flight and in a landing configuration.

Pick a point on the horizon, hold it steady, and very slowly change your angle of bank without letting the point move. Repeat this exercise while transitioning from an approach glide to level slow flight.

Add power as required to maintain a constant altitude while keeping that point steady. Now you are ready to start landing practice.

You learned how to keep the airplane from turning left or right in various angles of bank while flying in a landing configuration at speeds just above a stall by practicing SDR. This is a very good description of the technique used to land an airplane. If you
have a simulator, you don't need an instructor. That is the nice thing about simulators; you botch up and try again. Airplanes are not so forgiving.

In either airplane or simulator, here is how to learn to land. You have successfully flown the approach so you are about one wing span above the runway, over its center line and at just the right airspeed. From now on, forget about airspeed and PGP.
Looking forward and from side to side like you were driving on the open road, you start raising your nose to slow the airplane's descent. Using your rudder pedals you keep the nose pointed at the far end of the runway. Using your ailerons you keep the
airplane centered over the runway. Use your pitch attitude first, and then throttle, to keep the airplane off the runway.

You are NOT going to land! This is just an exercise. The objective is to get as close to the runway, at as slow airspeed as possible, without touching it. You are now doing that SDR in level slow flight that you did earlier. Just to prove you have mastered the
situation, slide the airplane from side to side just above the runway without touching but as close as you can get. Be certain that you continue to keep the airplane pointed at the far end of the runway and the airplane's body parallel to the runway. As you
approach the end of the runway, smoothly apply full power and execute a go around.

Each time you do this, fly the airplane as slowly as you can. Keep that stall warning screaming. It is really a fun thing to do.

As you develop skill with this maneuver, try touching the runway but without landing. Touch it very gently but at as low a speed as you can. At some point you will realize that all you need to do is to touch the runway very gently at a very slow airspeed, then
close the throttle and you will have landed. Easy, wasn't it?

Private Pilot Training Online focuses on the little things that hold pilots back; dispels the myths that make learning and flying unnecessarily difficult; and makes the ‘hard’ subjects easy.

Douglas Daniel, long time flight instructor, invites you to visit at http://PrivatePilotTrainingOnline.org for more flying articles like this one. You may also feel free to contact Doug by visiting his website.

Three Most Dangerous Landing Mistakes Pilots Make and How to Prevent Them

Over-shoot, under-shoot, loss of directional control, wing tip strikes ... are all symptoms of mistakes made BEFORE the pilot touches down. Mistakes that are easily prevented - but not necessarily in a way you might think.

I landed at the Nuttree Airport in a Cessna 172 in 1968. I felt pretty smug. It was a very smooth landing, one of those landings that you could hear but not feel. Then a wind gust picked me up and I landed a second time on a parallel taxiway. The pilot
taxiing in the opposite direction was kind enough (or perhaps stunned enough or frightened enough) to hold short of a turn-off so I could move over to the parking apron. I couldn't look him in the eye as we went past. I mumbled some excuses to my
passengers that I didn't believe. I had just made the three biggest (and most common) mistakes a pilot can make when landing.

Determined to never let that happen again, I spend a great deal of time in the intervening 40 years thinking about how to prevent these mistakes. The NTSB says that a full 45% of the weather-related accidents are caused by crosswinds and gusts. I
believe it. It is time to introduce some little known techniques that help prevent these accidents. But first, we should look at their causes.

Landing too fast is caused by flying the approach too fast or trying to force the airplane to land before it is ready. The solution is to fly a consistent approach at the same airspeed, picking a safe projected glide point (or PGP), and controlling the PGP until you land. But hold the airplane a foot or so off the runway until the airplane nose has rotated up to the landing attitude. Hold that attitude until the airplane lands. That way you will land at the right speed.

Failing to cross control in a crosswind leads to ground loops, being blown off the side of the runway (the MOST common cause of accidents in the United States), wing tip damage, or, in my case, flying over the infield and landing on a taxiway. To put it simply, cross controlling is using the rudder to keep the long axis of the airplane parallel to the long axis of the runway and using the ailerons to keep the airplane positioned over the runway. This guarantees that you will keep the airplane moving
straight down the runway after the wheels touch.

Quit flying the plane before the plane is through flying is one of the most dangerous mistakes that a pilot could make. Its cause is lack of concentration. Its solution is good flying habits.

I was lucky at the Nuttree. If the crosswind had been coming from the opposite side, I could have been blown into a canal. Remember that just because the main gear is on the ground does not mean that there is no 'fly' left in the airplane. Also remember that if you keep the airplane just above the runway until it absolutely, positively will not fly any more, then it will an unusually strong gust to put it in the air again.

It is easy to be lulled into the bad habits that lead to these mistakes. When the wind is gentle and the runway is long, all will be forgiven. So the question is: how to keep these bad habits from developing? Let me introduce two exercises that have helped my students far more than I could have ever imagined. They are the 'very slow Dutch roll' and the 'controlled projected
glide' point. Neither is difficult or dangerous. Both simplify and strengthen any pilot's ability to land.

The very slow Dutch roll is a simple exercise done at a safe altitude. It teaches two very important skills. First the pilot learns to continuously move the stick and rudders to control the airplane as conditions change, and second, the pilot learns how to cross
control the airplane in the most extreme circumstances.

Here is how to do a very slow Dutch roll. Pick a point on the horizon and hold it steady as you change the angle of bank, airspeed and flap configuration. Maintain constant altitude. Change your bank very slowly. Continue to increase the angle of bank until either the aileron or the rudder is pushed to its limit. This is the angle of bank for the maximum crosswind that the airplane can land in. The cross controlled airplane slowly accelerates to the side for a minute or two. During this time, the pilot must move the flight controls continuously - an unanticipated benefit of this exercise when I thought it up.

Let me tell you about the projected glide point or PGP. When you approach the runway your eye will naturally gravitate toward a point on the runway that does not move in your field of vision. The phenomenon is much like when you are on a collision course with another airplane: it stays still in your field of vision but just gets bigger. Well, there is always a point on the ground where exactly the same thing happens. This is the point that you would glide to if you never made that last little flair to land. This is an extremely important concept that can save you many hours of landing practice. I never heard another flight instructor talk about it but I am sure that many pilots use this technique.

You can control the PGP with power and drag while keeping the airspeed constant. To move the PGP closer to you, reduce the engine's power or increase the airplanes drag - usually with flaps. To move the PGP away from you, increase the engine's
power or decrease the airplane's drag. Put the two concepts together to make consistent, safe landings. Once established on
final, use the center line of the runway as your reference point for very slow Dutch rolls. Use the ailerons to position the airplane on the extended centerline, the rudder to keep the long axis of the airplane parallel to that extended centerline. Move the PGP
to the same place every time. I recommend the runway threshold. Consciously continue cross controlling until the airplane slows to a taxi.

These two simple techniques will get you to the same place on the runway every time in a landing configuration that compensates for crosswinds or gusts until the airplane is going so slow that you can taxi to parking.

Private Pilot Training Online focuses on the little things that hold pilots back; dispels the myths that make
learning and flying unnecessarily difficult; and makes the ‘hard’ subjects easy.

Douglas Daniel, long time flight instructor, invites you to visit at http://PrivatePilotTrainingOnline.org for more flying articles like this one. You may also feel free to contact Doug by visiting his website.

 

NDB Approaches Made Easy

The NDB approach is the oldest instrument approach and the most difficult to fly. For
me, it is the approach of last resort. A non-directional beacon is a very simple AM,
low power radio transmitter located near an airport. It sends out a Morse code signal
that you can listen to for identification. That's all; no azimuth or range information.
The instrument that tells you what direction you are headed is the gyrocompass after it
has be aligned with the magnetic compass. The instrument that tells you where the
NDB is relative to your airplane is the automatic direction finder (ADF). The ADF
looks like the gyrocompass but the compass rose has a different meaning. 360° means
straight ahead of the airplane, 90° means to the right, and so on around. You have to
use both of the compasses to fly a successful NDB approach.

Let me set up a hypothetical and straightforward NDB approach. Assume that the
NDB is three nautical miles from the missed approach point (MAP); the wind is from
the northwest at 14 knots; the approach speed is 100 knots; the minimum descent
altitude (MDA) is 350' MSL; and the final approach course is 360° magnetic. The
approach procedure tells you to pass over the NDB at 950' MSL. The NDB also
serves as the final approach fix (FAF).

Knowing all this, you do some mental arithmetic. The 14 knot wind has a 10 knot
crosswind component and a 10 knot headwind component. We can see that the ground
speed on final approach will be 90 knots. Fortunately 90 knots is 1.5 miles per minute.
So if you must go 3 miles from FAF to MAP, the approach will take 2 minutes. The
FAF altitude is 600 feet above the MAP altitude, so the final approach vertical speed
should be 300 feet per minute (fpm).

Let's start after you have descended to 950'MSL and have turned inbound to intercept
the final approach course. You fly a heading of 30° until the ADF reads 330°. The
airplane is now directly south of the NDB. A turn to 360° puts the plane on a bearing
directly to the NDB and both the gyrocompass and ADF read 360°. As the airplane
approaches the NDB the crosswind component blows you off course to the right.
The ADF tells you that the plane is off course by pointing to the left of straight ahead
by a few degrees. You cannot turn the airplane by those few degrees and head directly
toward the NDB again and hope to intercept the inbound course because the wind will
just blow you off course again. You know that you need to turn into the wind to some
degree if you are to find the crab angle that will keep you on course to the NDB. If the
ADF told you that the NDB is 5° to the left, you need to turn to a course that is more
than 5° to the left of the NDB. Read this next paragraph very carefully. It is tricky.

You know that you must turn into the wind to compensate for its drift. The ADF told
you that you have moved to the right relative to the NDB. Therefore you must turn to
the left. If you turned 5°, you would be pointing directly toward the NDB. You also
know that you must be heading to the left of the NDB to compensate for the
crosswind. If you did not move any closer to the NDB during your turn, you might
turn 5° to the left of the NDB and be on a ground track that would take you directly
over the NDB. But you have moved closer to the NDB and you want to intercept the
inbound course before you get to the NDB so you have more time to fine-tune your
inbound heading.

You turn the airplane 15° to the left. Both the ADF and the gyrocompass respond. The
ADF changes from 355° to 010°. The gyrocompass changes from 360° to 345°. You
want to stay on that heading until intercepting the inbound course. You would like to
see the ADF change from 010° to 015°. You monitor the ADF to see if it starts to
swing back to the right. If it doesn't, you need to increase the correction angle. If the
needle does swing to the right, you will be on course when the ADF points the same
number of degrees but in an opposite direction from the apparent error on the
gyrocompass. In this case, the ADF would read 015° and the gyrocompass would read
345°. Once you are on course, turn right to a heading of 355°. That is based on the
belief that a 5° correction to the left is the proper drift correction angle. You continue
to fine-tune your approach heading all the way to MAP at MDA.

Here is a mental trick that works for me that you might try: When looking at the ADF,
I think of 345° as -15° or as 15° to the left of straight ahead. I visualize it as one big
mark and one small mark to the left of straight up.

As you approach the NDB, you stabilize the airspeed at 100 knots indicated airspeed
(KIAS). When the ADF starts to be extremely sensitive, you know that you are very
close to the transmitter and simply fly what you believe to be the best heading. When
the ADF suddenly reverses itself, you note the time or push a timer button. You
reduce power to a setting that should yield a 300 fpm descent. You continue to track
toward the airport, maintaining a very constant airspeed. You adjust the power as
needed to establish your 300fpm or slightly greater descent.

Ideally you should be at MDA before you reach the MAP, otherwise you may never
descend to MDA. You are very careful to never descent below MDA.
When the timer indicates that the plane has flown for two minutes past the FAF, and
you do not have the airport environment in sight, you must execute the missed
approach procedure.

Doug Daniel is a long time pilot, flight instructor, software engineering manager and author. His department developed the software for the out-the-window-displays for the space shuttle, F-117, RS-71 and numerous other exotic airplanes. His writing focuses on flying techniques designed to make flying easier and safer. If this was interesting, visit his website at http://PrivatePilotTrainingOnline.org .

 

Three Lessons from Steep Turns

I was asked the question, "How do I keep my bank angle and speed steady in 45 degree turns?"
 
While this question looks quite simple, it is a very good one. There are several very  useful concepts you can learn by understanding what happens in a constant altitude,  constant airspeed 45° bank.
 
Let's assume that you enter a left turn by coordinated aileron and rudder movement.  As your angle of bank increases you have to pull back further on the elevator control.  Once the bank approaches 45°, you once again coordinate your aileron and rudder movement to stop the roll and maintain a constant bank but you must continue pulling back on your elevator control.
 
Where you look now is very important. Most important is that you notice where the horizon cuts the top of the instrument panel. A quick glance at the artificial horizon will verify that you are indeed at 45°. In most airplanes, that tiny white ball in the center of the artificial horizon instrument will be just slightly above the instrument's horizon. But be careful: don't fixate on that instrument.
 
Now take a quick glance at the altimeter. Is it moving? Verify that the ball is in the center. Before you move any controls, look out the window straight ahead. Then adjust your angle of bank and pitch attitude. One more time take a quick scan of the instruments. Keep this scan going. But spend most of your time looking outside.
Notice that I did not include the airspeed indicator in your scan. It is not important. If you hold altitude and bank constant, your airspeed will settle down and quit moving.
 
Interestingly enough, your aileron and rudder controls are to the right of neutral even though you are in a left turn. When you turn left your right wing inscribes a bigger circle through the air than your left wing. So it must travel faster. Since it is going faster, it produces more lift. Of course, when the right wing produces more lift than the left wing the airplane wants to roll to the left. So you must deflect the left aileron down and the right aileron up. In other words, you must keep the aileron control slightly to the right of neutral in a left turn.
 
Now you know that airplanes are unstable in roll. The fact that it wants to increase its bank once a bank has been established and the airplane is turning tells you this. So it requires your input to keep the bank from increasing.
 
It may not be obvious but you are in a slight pitch up angle of attack. This is because your airplane must lift 141% of its weight. This increased angle of attack causes Pfactor. Just as you must compensate for P-factor in a climb, you must compensate for P-factor in a steep turn. That is why you must push on the right rudder pedal. So there you are: turning left even though you are keeping the rudder and aileron to the right of neutral. Steep turns to the right are not exactly symmetric to steep turns to the left. Pfactor persists. More times than not you will find that you are pushing on right rudder pedal in a right turn even though your aileron control is slightly to the left of center.
 
Steep turns, like any other regime of flying, require that you move the controls to adjust the airplane's attitude. You should not move your controls to some preconceived position but only to change attitude.
 
The absolutely most useful lesson to learn from tight turns is to fly the airplane by controlling its attitude not by moving its controls to some preconceived position. By comparison, the facts that you eventually put the controls in a position opposite to the direction of turn to maintain a steady bank and that an airplane is unstable in roll are just curiosities.
 
Executing steep turns is an important and useful skill to master. It is also an essential exercise when becoming familiar with an airplane.

Private Pilot Training Online focuses on the little things that hold pilots back; dispels the myths that make learning and flying unnecessarily difficult; and makes the ‘hard’ subjects easy.

Douglas Daniel, long time flight instructor, invites you to visit at http://PrivatePilotTrainingOnline.org for more flying articles like this one. You may also feel free to contact Doug by visiting his website.

Three Most Dangerous Landing Mistakes Pilots Make and How to Prevent The

Over-shoot, under-shoot, loss of directional control, wing tip strikes ... are all  symptoms of mistakes made BEFORE the pilot touches down. Mistakes that are easily prevented - but not necessarily in a way you might think.

 

I landed at the Nuttree Airport in a Cessna 172 in 1968. I felt pretty smug. It was a  very smooth landing, one of those landings that you could hear but not feel. Then a  wind gust picked me up and I landed a second time on a parallel taxiway. The pilot  taxiing in the opposite direction was kind enough (or perhaps stunned enough or  frightened enough) to hold short of a turn-off so I could move over to the parking  apron. I couldn't look him in the eye as we went past. I mumbled some excuses to my

passengers that I didn't believe. I had just made the three biggest (and most common)  mistakes a pilot can make when landing.

 

Determined to never let that happen again, I spend a great deal of time in the  intervening 40 years thinking about how to prevent these mistakes. The NTSB says  that a full 45% of the weather-related accidents are caused by crosswinds and gusts. I  believe it. It is time to introduce some little known techniques that help prevent these  accidents. But first, we should look at their causes.  Landing too fast is caused by flying the approach too fast or trying to force the  airplane to land before it is ready. The solution is to fly a consistent approach at the  same airspeed, picking a safe projected glide point (or PGP), and controlling the PGP  until you land. But hold the airplane a foot or so off the runway until the airplane nose  has rotated up to the landing attitude. Hold that attitude until the airplane lands. That way you will land at the right speed.

 

Failing to cross control in a crosswind leads to ground loops, being blown off the side  of the runway (the MOST common cause of accidents in the United States), wing tip  damage, or, in my case, flying over the infield and landing on a taxiway. To put it  simply, cross controlling is using the rudder to keep the long axis of the airplane  parallel to the long axis of the runway and using the ailerons to keep the airplane  positioned over the runway. This guarantees that you will keep the airplane moving  straight down the runway after the wheels touch.

 

Quit flying the plane before the plane is through flying is one of the most dangerous  mistakes that a pilot could make. Its cause is lack of concentration. Its solution is  good flying habits.

 

I was lucky at the Nuttree. If the crosswind had been coming from the opposite side, I  could have been blown into a canal. Remember that just because the main gear is on  the ground does not mean that there is no 'fly' left in the airplane. Also remember that  if you keep the airplane just above the runway until it absolutely, positively will not  fly any more, then it will an unusually strong gust to put it in the air again.

It is easy to be lulled into the bad habits that lead to these mistakes. When the wind is  gentle and the runway is long, all will be forgiven. So the question is: how to keep  these bad habits from developing?

Let me introduce two exercises that have helped my students far more than I could  have ever imagined. They are the 'very slow Dutch roll' and the 'controlled projected  glide' point. Neither is difficult or dangerous. Both simplify and strengthen any pilot's  ability to land.

 

The very slow Dutch roll is a simple exercise done at a safe altitude. It teaches two  very important skills. First the pilot learns to continuously move the stick and rudders  to control the airplane as conditions change, and second, the pilot learns how to cross

control the airplane in the most extreme circumstances.  Here is how to do a very slow Dutch roll. Pick a point on the horizon and hold it  steady as you change the angle of bank, airspeed and flap configuration. Maintain  constant altitude. Change your bank very slowly. Continue to increase the angle of  bank until either the aileron or the rudder is pushed to its limit. This is the angle of  bank for the maximum crosswind that the airplane can land in. The cross controlled  airplane slowly accelerates to the side for a minute or two. During this time, the pilot  must move the flight controls continuously - an unanticipated benefit of this exercise  when I thought it up.

 

 

Let me tell you about the projected glide point or PGP. When you approach the  runway your eye will naturally gravitate toward a point on the runway that does not  move in your field of vision. The phenomenon is much like when you are on a  collision course with another airplane: it stays still in your field of vision but just gets  bigger. Well, there is always a point on the ground where exactly the same thing

happens. This is the point that you would glide to if you never made that last little  flair to land. This is an extremely important concept that can save you many hours of  landing practice. I never heard another flight instructor talk about it but I am sure that  many pilots use this technique.

 

You can control the PGP with power and drag while keeping the airspeed constant.  To move the PGP closer to you, reduce the engine's power or increase the airplanes  drag - usually with flaps. To move the PGP away from you, increase the engine's  power or decrease the airplane's drag.  Put the two concepts together to make consistent, safe landings. Once established on  final, use the center line of the runway as your reference point for very slow Dutch  rolls. Use the ailerons to position the airplane on the extended center line, the rudder to  keep the long axis of the airplane parallel to that extended centerline. Move the PGP

to the same place every time. I recommend the runway threshold. Consciously  continue cross controlling until the airplane slows to a taxi.

 

These two simple techniques will get you to the same place on the runway every time  in a landing configuration that compensates for crosswinds or gusts until the airplane  is going so slow that you can taxi to parking.

 

Private Pilot Training Online focuses on the little things that hold pilots back; dispels the myths that make learning and flying unnecessarily difficult; and makes the ‘hard’ subjects easy.

 

Douglas Daniel, long time flight instructor, invites you to visit at http://PrivatePilotTrainingOnline.org for more flying articles like this one. You may also feel free to contact Doug by visiting his website.

 

Airplanes Don't Stall, Pilots Stall Them: The Myth of Stall Speed

When smooth airflow separates from your wings they stall losing most of their lift. If you are lucky the airplane drops like a stone, pitches forward, accelerates and starts to fly normally again. If you are not so lucky, one wing stalls, rolling your airplane toward the stalled wing as it progresses to a spin before you can recover. It is probably a good idea to keep the airflow attached to the wing and the tail and every other aerodynamic surface needed for controlled flight. An aerodynamicist would tell you that stalls can only occur when an airfoil reaches or exceeds its critical angle of attack. I would say that a stall occurs only when you try to make the wind turn too sharp a corner.

You see, air is sticky. Not very sticky but it is a little sticky. An aerodynamicist would clear his throat; raise his eyebrows and say, "Viscous." So let's ignore the aerodynamicist. It's sticky. When air blows past a gently curved surface, like a wing, it tends to stick to the surface even though the surface curves away from the wind.

If the wing is symmetric top and bottom and the wind is coming straight on, the wind impacts the front of the wing and builds a high pressure area there. Then as it starts to follow the contour of the wing, like anything following a curved path, it gets pulled out. But its stickiness holds it on the surface. The result is low pressure over most of the surface, top and bottom.

Now if you pitch the wing up a bit by pulling back on the stick a bit, the air on top must change direction a bit more than the air on the bottom. The result is more low pressure on the top and less on the bottom. Perhaps the high pressure area on the bottom of the wing is bigger than before. The wing is sucked up by the top and pushed up by the bottom. We call this lift. Suppose you pitch the wing up a lot by pulling back on the stick a long way. The air on the top has to change direction a lot and the pressure on the top drops a lot. If you pull the stick far enough, the low pressure area on the top of the wing sucks air from the back of the wing forward, separating the airflow from the top of the wing. This is bad. The low pressure area on the top of the wing disappears as it is filled by the forward flowing air. The wing loses lift. This is a stall.

The airflow separates from the wing of a properly designed airplane before it separates from the tail. If the tail has lift and the wing doesn't the airplane's wing drops and the tail doesn't. This is a good thing because the wing comes down and faces a lower pitch attitude. The results are that the wind re-attaches to the upper surface, lift is restored and the airplane returns to normal.

Now, suppose the pilot continues pulling back on the stick. As soon as the wing develops lift, it goes up too far again and stalls again. We call this bobbing action 'buffeting.' Buffeting is good because it warns the pilot that he or she is pulling too hard on the stick and the wing is ready to enter a serious stall - one that could lead to a potentially fatal spin.

So now we know that the real warning of an impending serious stall is buffeting. We also know that buffeting is caused by pulling the elevator control too far. So we know that the way to avoid a stall is to pull less when we feel buffeting. We also know that if we pull less on the elevator, that the airplane will go down. That could be a really bad thing. Increasing the engine's power simultaneously with easing up on the elevator can mitigate that sinking feeling.

Notice that no where in this discussion of what causes stalls and what to do about them was the concept of airspeed needed. Stalls are only caused by pitching the wings up too far - nothing else. Even though stalling speed is a useful term, there really is no unique stalling speed for an airplane. You have to read the fine print. What 'stall speed' usually means is the speed at which an airplane's wing exceeds its maximum pitch attitude when the airplane is loaded to maximum landing weight, is in the landing configuration and flying straight ahead.

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