mushing on final
 

In "Stick and Rudder" Langewiesche asserts that if too high on final one should raise the nose instead of the instinctive lowering, so that the airplane would "mush" and lose altitude. I have tried both of these methods and have a couple of questions/concerns about mushing. I have "mushed" on final only when an instructor was on board and have always lowered the nose and added flaps (if not already done so) when flying solo. I feel like raising the nose on final creates a dangerous situation in which a decrease in airspeed, and AOA, are a perfect recipe for a stall. Mushing on final feels at least for me to be a maneuver that requires quite a bit of finesse and if not done properly could lead to an unwarranted situation.

I don't teach that at all...
Power for altitude, pitch for airspeed

x2

Looks like you have a good understanding of stall/spin awareness, PearlPilot.

I remember reading that book when I was a CFI and thinking, "Wow, we've learned a lot about basic aerodynamics since this was written!"

Although a classic, using Stick and Rudder as a primary source is a bit like a med student reading a Biology text written in the 1940s. Look up something written more recently.

* This should not preclude one from spending many nights pouring over Aerodynamics for Naval Aviators (it doesn't get any better than that), but save that for your CFI.

You do mean a decrease in airspeed and an increase in AOA is a recipe for a stall - correct?

USMCFLYR

Sounds to me like they are talking about performance landings and ground effect. Instead of diving for the spot if you're to high, the best thing to do is maintain or slightly increase your angle of attack which allows you to fly through ground effect with the least amount of float. In contrast if you're low and have obstruction clearance the best thing to do is pitch forward to carry speed into ground effect and maximize your float to your spot.

I unfortunately disagree, his dynamics were pretty spot on. Mushing gives you the steepest feasible glide slope, thus the shortest landing distance.

Disclaimer: Mushing in at stall is for 0.00001 percent of pilots in very rare situations. Don't be a retard, this isn't a save a bad approach maneuver. You perform this only when you have absolutely no other option available.


Only if you are below best glide speed. Despite what is said about diving for ground effect it doesn't help you increase your range. This is especially true in high wing trainers like the Cessna as they get far less benefit from ground effect than their low wing Piper counterparts.

The loss of performance by increasing speed above best glide counters the slight benefits of reduced drag in ground effect. The result? A useless maneuver that, if used in a real engine out scenario and misjudge, could do more harm than good.


To the OP: He is right about mushing being better than diving. There is a key to this though, the key is he is right when speaking in terms of maximum performance. You have to weigh your skills as a pilot versus the ability to utilize the aircrafts full performance capabilities.

I would recommend reading the book Emergency Maneuver Training by Rich Stowell. He does a nice job explaining the relationship of the power required curve to a glide.

The concept is still basically sound, although I wince at "mushing."

Basic short field over obstacle landings involve a slower airspeed and higher descent angle (behind the power curve) than a "normal" landing. That's produced pretty much as Langewiesche described.

Yep, when high on final, I definitely get (and teach) the airplane into a short field obstacle descent configuration to increase descent rate and angle while keeping airspeed from increasing too much.

It's fun to watch the alternative. Nose down to the spot, increasing airspeed even with power at idle, and an overshoot because the airplane has way to much energy when it gets to the runway.

Notice: not one word about whether pitch or power is for airspeed or descent rate.

On my CFI initial the inspector was, albeit, bothered that so many instructors teach pitch for airspeed, power for altitude when demonstrating landings.

He took the plane from me and said "Watch...pitch for the runway, power for speed. And this works in ALL airplanes."

Needless to say I now only mention the power curve when teaching slow flight.

Thrust to Weight Ratio
 

I've been taught both ways (civl and military). The primary difference was about thrust to weight.

Light aircraft are generally pretty low-powered. Often times, the only way to speed up is by lowering the nose.

High-performance jets (fighters) generally don't have that problem, although when maneuvering well beyond the stall, even burner won't accelerate in some circumstances. Civil jets can easily have the same problem. (Think heavy airliner, fully-flapped, slow on final...thrust isn't totally effective to speed up if on the back-side of the power curve.

In any airplane, the real answer is: it's both. It depends on how far on the back-side you are, and whether there is adequate thrust to speed up. I primarily use throttle for speed, pitch for vector control...unless I run out of throttle.

Yes that is correct. My apologies. I have also found out that in the times I mushed, I only had to raise the nose a little bit. For an example on the old 172, for a short field approach I use 65 mph, on final, and if a little too high, I would not get slower than 60, and it works perfectly. But like I said before, I believe that it takes a great deal of skill and confidence to do this when you are so low and slow.

"mushing" or whatever it's called... is probably a better/easier/safer technique than a forward slip. IMHO

mushing may easier and safer for you, but I would never teach that to a primary over a forward slip. The main thing that worries me in this case is airspeed control / coordination. Also if you hit a windshear that decreases headwind, there's not much of a margin from stall even for some of the more experienced pilots.

You also have to realize that in stick and rudder they are likely talking about J3 cubs or luscombes or old T Crafts, not your run of the mill trainer as recent as the 70s.

In todays modern planes if you find yourself high on final and are on speed you can simply "dump" a little more flap to increase your descent rate while maintaining airspeed with pitch or power (your choice).

"Mushing" (what a stupid word) is truly a back country/short field technique. You can come in higher than normal and get "closer" to the field bypassing the 3 degree glide path and come in closer to a 6+ degree glide path also known simply as being high on final. Once you hit the designated point where you are high you can cut the power back a bit and raise the nose to a near stall airspeed and then maintain your glidepath with power riding the backside of the curve the whole way down. Finish off with either what little flare you have left just before touchdown and/or a small burst of power to arrest your descent. This nearly eliminates float as well as puts you on the ground with little forward energy at the slowest speed possible.

The same technique is what they are mentioning but they mention it in the book merely as a way to get down when you are high.

Personally in a J3 or flapless airplane if I have no need to use less than 400 feet of runway I will use an appropriate well timed slip which will do everything I need and then some. In a slip it is very easy to control both descent rate as well as airspeed and is a bit of an ideal technique IMHO.

As a primary student, first off all, kudos for reading that book. There are some great things in that book that still ring very true today. Take some of it with a grain of salt though as they may not be an ideal technique in todays modern realm of flight. I would not recommend any student raise the nose and mush down final anywhere near stall. I would push my student to simply fly a configured approach on profile and instead of teaching them to save it I would teach them to go around. You can learn to save it as you gain experience.

Why? A slip is stable, try stalling in a forward slip in a 172.


To those discussing pitch/power:

It isn't about how you do it, how you do it is fine. However, the student, and you, should understand what is actually causing the change. When you add power it isn't the power that caused the change in speed.

This doesn't mean you can't teach someone to add power when speed is low, you can and should. But you should tell them that when they increase power they have to pitch forward to prevent a climb, that pitch is what actually controlled their speed.

Power will never, has never, and can never control speed in an airplane.

IMO every pilot should know two rules about climb/speed control:

1. Excess power controls descent/climb. This happens in 2 ways:
   • Changing the power setting
   • Changing the speed resulting in a change in power required
2. AOA controls speed.

Disclaimer: These two "rules" as I like to call them come directly from mathematical formulas. If you wish them posted and explained just ask.

How you apply it is up to you. However, telling a pilot that power is giving them speed is like me telling you that a ball bounces because the ground doesn't like it. Teach them the truth and then teach them your method of applying that truth.

In retrospect I see your point... I've used the slip a fair amount of times in a tailwheel - but usually it's just limited to tailwheel...have never really needed it other than crosswind. The "mushing" is like usmc-sgt said a back country technique for short strips. You can come in stabilized at a slower speed than say a slip... but it's all different strokes for different folks, whatever floats your boat....

The danger I see in a slip for a primary guy is getting a really high descent going, and then instead of releasing pressure, just pulling back on the yoke/stick to arrest the descent and ...

In the Caribbean, the 'mushing' (can we call it something else?) technique seems to work coming over the ridges and mountains to a small runway. The aircraft really isn't that close to a stall, even if you did start to buffet you can just drop the nose a little and/or add a bit of power.

Now, I wouldn't use this technique in a twin.

If you're high and below best glide, then reducing power and increasing backpressure would produce a steeper descent. Reducing backpressure would bring the airspeed closer to best glide and essentially produce a shallower descent (the airplane will initially appear to decrease its rate of descent). Experiment with this at altitude, and you will see that it is strangely true.

Never Use Absolutes....
 

Don't know your background, but I'd guess you haven't done a lot of zero-g flying.

Scenario: going straight up (or straight down) at zero g: Power has a significant effect on going fast or slow. (Been there). ;)

Very true. Absolutes are a favorite of those who dwell in theory and formulas, but in fact pitch and power are required in combination to get to a speed.
In cruise, power is the primary means of setting speed, with a very minor variation in pitch. In descent at idle power, pitch becomes primary with power fixed at idle. On a normal glidepath power is used as the primary control with very minor variations in pitch.

The key here is that both AOA and power always work together to give you a speed or desired performance.

More or less true. It never ceases to amaze me the almost-religious zealot fervor with which people argue this non-issue.

So what is a "mush" and what really happens to the airplane (aerodynamically speaking) in a mush?

A mush is a non technical term for flying at a high angle of attack near stall speed.

The aircraft "mushes" through the air and the controls feel "mushy".

Its all very technical of course.

To mush or not to mush, that is the question.
 

I think we have missed a very important point here, especially as it relates to teaching landings. The correct procedure, in my opinion, is to maintain a stabilized approach below 500 feet agl to touch down in the first 1/3 of the runway. If this isn't possible, go around and try it again or go somewhere else. Yes, that includes short strips. If you can't do that at the short strip you are trying to get in to, go somewhere else and rent a car!

Before I get started I am trying to be as objective as possible in the upcoming post. I mean no disrespect and have attempted to keep things relatively indirect. Keep in mind I am still presenting a case and doing so with conviction.

I call this a case because it a century old debate where I believe each side stands to benefit from a solution. Below you will find misunderstandings for those against using a singular ideas, an explained example, misunderstandings of those that are for a singular idea, and a conclusion with some final thoughts on human change.

Again, I am attempting to find a common ground. So please try to read this as it is intended: as an objective opinion on a compromise and not as a personal attack to anyone's beliefs.

Thank you: Here we go...


Misunderstanding(everything controls everything group) #1:


I know many of those on the "everything controls everything" side will say something similar to this regularly. In my opinion it demonstrates one of the two ways this group lacks understanding. Let me show you:

This group often will give an example that demonstrates their academic understanding of the topic. However, it is my belief that they take this knowledge for granted. Not in a bad way, just that it isn't something they think about. For instance, if you are taught to type on a keyboard do you still have to think about how to hit the "q" key?


This shows this pilot understands how this works. Furthermore, knowing that only few aircraft can perform this, this pilot is either military, NASA, aerobatic, or aerobatic instructor.

This was the knowledge I mentioned that is likely taken for granted. Now let us answer a couple questions using information taken from a military textbook, "Aerodynamics for Naval Aviators" without using formulas:


Question: What controls rate of climb?

Answer: "The above relationship states that, for a given weight airplane, the rate of climb (RC) depends on the difference between the power available and the power required (Pa - Pr), or excess power. Of course, when the excess power is zero (Pa - Pr = 0 or Pa = Pr), the rate of climb is zero and the airplane is in steady level flight.

Page 154.
Further information on Page 350: Read the section titled "Rate of Climb and Descent."

Question: What controls speed?

Answer: "This fact provides a fundamental concept of flying technique: Angle of attack is the primary control of airspeed in steady flight"

Page 27.
Further information on Page 350: Read the section titled "Angle of Attack Versus Airspeed."

For basic aerobatics, a man named Rich Stowell wrote a book "Emergency Maneuver Training." His responses to these questions, though not identical wording, speaks to the same theme military textbook.


Misunderstanding(everything controls everything group) #2:


On the flip side, the pilot that doesn't understand because they were not taught it, forgot it, or don't see its relevance/importance. These pilots make claims that are completely untrue and pass these claims onto the unknowing/unsure pilot. Such as (Name of quote author intentionally left out.):

Power is not required to gain airspeed. It is only required to maintain level flight or a constant rate of descent when airspeed is changed. A change in airspeed slides you left or right on the power required curve, changing the power needed to maintain a given condition. If that change in AOA is made in level flight, causing a change in airspeed, and not met by a subsequent change in power then a climb or descent will result.

You may think in your head, "pitch forward and add power gives me speed" and that is your application, your technique. However, you should know which action, the pitch or the power, gave you the change in speed.

This next statement shows the author of this quote knows two things are happening. He/she likely knows what is controlling which. What they don't understand is how this statement can screw up a student:

I underlined this because it is important in this next part. While this pilot might understand how all this works, there is no guarantee that regurgitation such a statement will result in the student having an equal or even proper understanding. Have anyone ever had someone tell you something and what you heard wasn't what was said?

This is both taught and discussed in the CFI course, the topic from the CFI text is communication. We also discover barriers to communication. Of the barriers the one cited as most prevalent is "lack of common experiences." In the example of regurgitating this statement to a student, you are exhibiting knowledge from experience (the resultant small pitch changes). There is no guarantee the student will receive that same experience or that they will draw the same conclusion as you or have matching perceptions.


An Example:


Imagine on the debrief you give them this statement verbatim as quoted. In the air you give a student the controls and say, "ok check the airspeed, now look at the horizon, and now add power..wait a few seconds. Now look at the airspeed again. What do you see?" and the student replies, "The airspeed went up."


Possible Outcomes:


Now the intuitive student will say something along the lines of having to add forward pressure. The savvy instructor would meet this topic on the ground with the debrief, ensuring the student understands why that action happened. The answer by this savvy instructor wouldn't be, "you had to pitch down because you added power" because he/she knows that statement is untrue.

The less intuitive student will likely not notice or mention the stick pressure. By not mentioning they quickly forget of its existence. The new CFI, any CFI unfamiliar with these dynamics, or the CFI who doesn't believe it to be important will be less likely to recognize this situation.

Did you catch the situation?

Student was told: "In cruise, power is the primary means of setting speed, with a very minor variation in pitch."

Student sees: "In cruise, power is the primary means of setting speed, with a very minor variation in pitch."

Unless the student & instructor debriefed the change in pitch experienced in this scenario, explaining the reality of what occurred, the student will act by what he saw and not by what was heard. For each flight after where it isn't addressed they make an action (in their head one action) to add power and see an increase in airspeed. They will continue to see this one cause giving one result and now power controls airspeed in their world, but not in reality.

Similar issues happen when pitch is taught for glide slope (altitude) and the control inputs are not addressed.

These students are deprived of a basic right to them as pilots, IMO. The right to know what each basic aircraft control will affect their aircraft.


The Rules Restated:


In my previous post I gave two rules and said, "How you apply it is up to you." Meaning, use your own technique but still explain what is happening and make sure they understand the reality. This is the reality (except in 0g flight :rolleyes:):

1. Excess power controls descent/climb. This happens in 2 ways:
   • Changing the power setting
   • Changing the speed resulting in a change in power required
2. AOA controls speed.

Misunderstanding (the absolute one rule group):


This group doesn't see the benefit to having multiple ways to do things. That or they do things multiple ways without realizing it. The result is, like their counterpart takes knowledge from their training for granted, this pilot takes for granted their knowledge of application (his/her experience).


Conclusions:


Desire for consistency (to settle) is the one human trait that makes compromise near impossible. If nobody will change because it means leaving a known for an unknown than nobody will ever expand beyond the knowledge they know today. Without a change in behavior, mental or physical, learning cannot exist.

On one side is the argument that we know what is happening, why don't we teach it? On the other side is the argument that everything is situational. My argument is why can't situations include simple control input understanding, using the rules listed above.

I believe that using these rules when explaining scenarios improves instructors/pilots on both sides of this argument. The instructors on "anything for anything" side can reaffirm their understanding of basic controls, likely improving their own application and teaching of basic controls. Conversely, the instructors stuck on "one way for all" can learn other ways to apply techniques. They can even learn to teach the various techniques while still keeping the truth of reality in their explanations, an experience that will likely better their application and teaching of basic controls.

So there it is, we aren't all that different after all. I for one would think that we can both benefit from learning how to accurately teach both techniques without degrading a students understanding of basic control input in the process. This requires teaching them these rules but allows the technique to be flexible in the process.

Help me find something that makes both sides change while keeping both sides happy. What do you think? Please, all criticism is welcome. You may send it here or to my gmail [email protected].


Thank you all for reading. A few weeks of thought and testing has gone in to the presentation you see here today. Help me perfect it and thank you again,

~Brian


***Disclaimer:*** My argument is no longer that pitch (AOA) for airspeed and power for altitude is the only way. My argument is that whichever technique is decided upon it should not be at the expense of a students understanding basic aircraft control.

Well if you we the airplane pilot handbook which is a faa pub it does say in reference to forward slips which are meant to loss altitude that you should simply do a go around and set up a stable approach.

"IMO every pilot should know two rules about climb/speed control:

1.Excess power controls descent/climb. This happens in 2 ways:
◦Changing the power setting
◦Changing the speed resulting in a change in power required
2.AOA controls speed."

It is the mark of a fundamentalist to speak in absolutes. I can easily change the speed at a fixed power setting(climb or descent) with pitch.

Try flying a 3 degree glideslope using AOA only without any power change, doesn't work in the real world. Both AOA and power are required in real world situations to control speed and performance.

Textbooks simplify this point, but don't take into account the interaction between the two. If AOA is fixed power has to change, if power is fixed AOA has to change to get the desired performance at the extremes-but between the extremes there is a blending of the two.

I was reading Aerodynamics For Naval Aviators(on the way to becoming a Naval Aviator) when you were still in diapers, or perhaps a gleam in your fathers eye. I also have years of instructor time in Military jets.

The two factors interact, even more so when you are pulling six g's or negative g's.

That statement displays an invalid assumption (aka "belief") on your part. There's a touch of arrogance in the statement as well.

In my case, I think I understand the concepts fairly well. And I don't teach "everything controls everything." That's not a way to bring a fledgling pilot from the the two-dimensional world of cars to the 3-dimensional world of the air.

I teach one of the two methodologies - the one I personally think makes the most sense as an initial teaching technique to achieve the ultimate goal of coordinated use of pitch and power to control airspeed and vertical rate.

But I'm not arrogant enough to think that mine is the only right way to reach that goal. So I don't argue the issue with zealots.

Compare

==============================
Power setting. Before entering the climb or descent, choose a power setting and estimate the amount of pitch attitude change required to maintain the airspeed.
==============================
with
==============================
Maintain vertical velocity and airspeed. Rate climbs and descents are accomplished by maintaining both a desired vertical velocity and airspeed. They are proficiency maneuvers designed to practice the techniques used during instrument approaches. Pitch attitude controls the desired vertical velocity, and power controls the desired airspeed.
==============================

Both are from the same source. And yes, in one case they are talking about constant rate climbs and descents and in the other constant airspeed climbs and descents. But the bottom line is that the authors of that volume reject a one-size-fits-all approach based on dogma.

Back to Original Post
 

shdw:

I have Aerodynamics for Naval Aviators, and it is an excellent text. But it was also written in the late 1950s, and there is an addenda that must be referenced.

If you are familiar with the drag-curve (and I'm sure you are, judging by the aero equations): light airplanes are low-powered. While flying on the backside of the curve (landing approach), if one gets slow enough, the drag required can exceed power available. The airplane will slow. The only way to speed up will be a reduction in AOA.

Sailplanes/Gliders: the only motive-force is gravity, and if one gets slow enough, the drag will exceed the component of gravity in the direction of motion. The only way to speed up will be a reduction in AOA.

Fighters: up to 3rd Generation, even afterburning jets can get slow enough that full thrust can be less than the total drag. The only way to speed up will be a reduction in AOA.

5th Generation fighters (F-22; Flanker) or F-16 Block-50 with big inlet: these aircraft have so much thrust available that at minimum controllable airspeed and maximum AOA, the aircraft will accelerate with power alone. This type of thrust-to-weight ratio did not exist when Aero for Navy Guys was written: an airplane that can generate more thrust than drag, at any airspeed or AOA. :eek:

In Max thrust, an F-16 Block 50 will accelerate, even when pulling 9 g's (high AOA and near maximum drag). (I guess thrust doesn't control airspeed). :rolleyes:

As I said before, it depends on the thrust-to-weight ratio of the aircraft as to which technique(s) work.

Pitch to control speed works pretty well in light airplanes. A combination of Pitch/AOA/Throttle works pretty well in medium to high-powered airplanes. In extreme powered airplanes, the combo still works, but at the extremes, power controls speed.

So what do you tell the student who is flying a Lake Amphibian (with the propeller far above the wing) is happening when he adds power during stable, level flight? In this case the airplane pitches down and the student has to increase pitch to maintain level flight.

In most light trainiers and most airliners, the center of thrust is below the center of gravity. This means the aircraft will pitch up as power is added, and down when power is reduced. Not all aircraft are configured that way, however.

Apologies, I should have mentioned this in that first post. The points made here apply to all aircraft, but I speak in terms of general aviation flight instruction. Not for military or commercial.


Wouldn't this change in speed with pitch cause the climb or descent to no longer be constant? Why would the climb or descent happen when you use pitch to change AOA to change speed?



I am unsure the point. Does this mean you understand it better because you read it 30 years ago? :confused:

It's funny, you read that entire post (maybe?) and got nothing out of it. You'll never get anything out of something if you approach it with this kind of attitude. Dismissive and pompous.

You quote the 2 rules I listed that come directly from formula's that I will show and work through if necessary. Then you go off on a rant on how you can break those simple rules. You cannot say it doesn't happen like that, that is how it happens and I will post multiple sources and more books if necessary. How you want to apply it is up to you, like I've said many times now, but the rules for what happens from each input remain constant.



Not an assumption. I've discussed this topic at least 5 times in the last 6 months. Every time this cycle repeats.

Did you read the bolded misunderstanding #1? Let me repeat one key section, "This group often will give an example that demonstrates their academic understanding of the topic." I believe you understand the academics, but I think you might take some of that knowledge for granted.

I think you have the right way to do it. So long as you ensure the student understand the reality of a control input, not just the perceived reality.

So what was this post? I said, "Keep in mind I am still presenting a case and doing so with conviction." I don't get why many of you seem so offended. Maybe I'm just crazy?

They give techniques and appear to avoid aerodynamic reference. Hmm...are they FAA books? If you read my post you would know my argument has nothing to do with the technique used. Teach any technique you want, but in the process ensure your student knows the reality of the input.



Do you think that changes the two questions I used that text to answer? Would you mind explaining how?



Explain the thrust lines relationship to the cg line.

"It's funny, you read that entire post (maybe?) and got nothing out of it. You'll never get anything out of something if you approach it with this kind of attitude. Dismissive and pompous."

Sorry you feel that way, but I can understand why. My point is that what you are talking about is not new or unique in content, but it is in fact a distorted view of a few facts you have collected seemingly at random, and by stuffing a few facts into a whole bunch of verbosity that really doesn't have much to do with what we are discussing you now want to call it new or unique.

The last time we chatted you claimed to have developed a unique crosswind method for twin engine aircraft of all sizes. Despite Boeings recommendations to the contrary you wanted to encourage pilots to use this method at the risk of their lives, their passengers lives and their shiny new 200 million dollar jet. It didn't go over too well.

I am always ready to learn, but don't think you can urinate on my back and convince me it is raining.

Just a little tip, if you want to teach people something keep it short and simple. Your students will learn faster by doing than by mulling over pages of formulas.

How many students are you working with now? If a student disagrees with your opinion, do you call him dismissive and pompous or try to teach another way of looking at the situation?

I ain't gettin' into this one. I don't get paid enough, and all the retired military trainers are here anyway. Good luck, shadow. :)

I'm done here too.:D

US Air Force Instrument Training Manual.