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don.olandese

Well Known Member
Practicing/de-rusting the other day in a spam can, instructor wanted me to - upon simulating sudden complete loss of power in cruise - immediately raise the nose to gain a hundred or two feet of altitude - i.e., zoom up to maximize altitude - before initiating the rest of the emergency procedures (check stuff, establish proper pitch and glide speed, etc). I suspect that gaining the altitude at engine-failure is less beneficial than simply allowing the airspeed to bleed off gradually, THEN pitching to proper best-glide etc. i think that because the induced drag during a sudden climb should be comparatively greater than during a gradual deceleration. The POH just says "establish pitch attitude for best glide:" no details on whether to slow the airplane with a climb or let it slow down gradually in level flight, which is how i've been doing it for years. Comments, references, wild-*** opinions? whatever is the right answer probably applies to a lot of different airplanes, including our favorites...
 
For almost every instructor in the world there is a different technique, or pet subject.

In this case I would be currious of the experience of the instructor (IE new guy and doesn't know, or old guy with wierd reason), and just plain ask why do you think this is required?

Your reasoning certainly falls into line with my thoughts on the subject.

My personal first response to an engine failure is carb heat while simultaneously pitching to best glide. (I understand some RV's don't have this so moot point in them) The reason for this is to not loose any heat doing something else first.

I knew one pilot that back in the day, actually told an examiner during a flight test "The exam is now being suspended, I have control." Landed the airplane and told the guy that his services were no longer needed and he would never land a multi engine airplane with one engine shut down unless it was an actual emergency. A argument ensued and both walked away thinking the other was crazy. It was later rumored that the examiner did eventually stop requesting the engine shut down landing during his exams.

Mark
 
Hi Don....

...that kind of thinking is with tunnel vision. I've had two engine failures...one, a radial making metal and another, my Supercub fuelled with a gallon of water!

Pulling up with no regard for what's below you is a knee-jerk approach...the first things should concern you over why the engine quit. Ice, fuel starvation or a blown engine and so on, with appropriate action on your part....carb heat, fuel selector changed to the other tank, fuel pump on, etc.

You may be over or near an airport and don't want or need any more altitude, or a suitable pasture or open field.

Best,
 
Just ask why! I have my flight students ask lots of great questions. It's actually a way you can evaluate the learning process. Asking questions is vital to being a good student. Talk it through with the instructor. You might actually change his (or her) mind or help you understand.
 
The lift/drag ratio varies with the angle of attack (AOA). From a pure theoretical point of view, you'll get the absolute maximum glide range if you are at the AOA for best glide the whole time (assuming zero wind). So, if your speed at the time of engine failure is above the speed for best glide, you would want to pull up to increase the AOA to the AOA for best glide. Thus you would climb, trading speed for altitude. You would arrive at the speed for best glide pretty quickly, and then transition into a glide at that speed.

The difference in glide range between the optimum pull up at AOA for best glide, and just holding altitude while the speed bleeds off is probably fairly small, unless the airspeed was very high when the engine failed. In the real world, you have a lot of other things to do to, such as picking a forced landing field, doing the engine failure checklist, declaring the emergency, etc.
 
i asked why...

the instructor's logic seemed good: why fail to gain altitude you could gain while attaining best glide? i haven't found FAA procedural guidance that detailed yet, so still welcome more ideas. it just seems better to fly the airplane most efficiently as it slows, which means in the least-drag configuration vs climbing. of course the rest of the emergency landing procedures continue, but there seems to not be a consensus on what to do/how to maximize our advantages during the time between power failure and attainment of best glide. thanks for the comments, past and future!
 
So... do you
(a) cover more ground distance and/or
(b) stay above the ground a longer time

when you either
(a) pull up (zoom) to best glide gaining as much altitude as possible or
(b) bleed off speed to best glide while maintaining altitude

...as others have said, I bet those curves are pretty close to each other. And the affects would average out further if the glide was very long...the zoom would probably be most useful if you were flying low at high speed...which I've seen help in some military bailouts.

However, pretty easy to do live tests at altitude and see what happens in a particular plane...sounds like something interesting to do the next time I'm bumming around by myself. :) (I drove my CFI's a little nuts testing what they told me or was "common knowledge" at altitude...but we both learned a lot.)
 
Energy management

This is a question of energy management.

http://www.av8n.com/how/htm/energy.html

Ignoring friction losses (love that simplification!) gaining altitude or maintaining airspeed won't add or subtract energy.

Judging from the number of stall/spin crashes, it could be argued that that many people have trouble responding to engine failure, particularly right after takeoff, so I would have to question the wisdom of advising students to pull back on the stick/yoke during an engine failure. I was trained that the first reaction to engine failure, no matter the flight regime, was to push the stick forward, then start playing around. I believe this training was to help students overcome the instinct of yanking back on the stick and stalling.
 
Energy Management

Thanks Mickey, you saved me from writing a long tome on energy management. Well done!

John Clark ATP, CFI
FAA FAAST Team Member
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
Kevin Horton said:
---- you'll get the absolute maximum glide range if you are at the AOA for best glide the whole time (assuming zero wind). So, if your speed at the time of engine failure is above the speed for best glide, you would want to pull up to increase the AOA to the AOA for best glide. Thus you would climb, trading speed for altitude.
Click to expand...

Yep.

This is exactly what Reno racers do when something goes bad.

But then, Reno racers have a lot of excess speed above the best glide speed.

When you have the excess speed, trading it for altitude is good practice IMHO.
 
As a point of reference, the zoom to best glide is what we taught in T-34's in the Navy. Having said that, I agree that the difference in efficiency between that and just bleeding off A/S while staying level is probably negligible in a practical situation. The author in Mickey's link does point out that the higher parasitic drag at higher airspeed does tilt the efficiency towards the zoom climb (see chapter 15 of the article).

Speed has a lot to do with it = nothing gained by zooming off 10 kts. If in cruise, I suggest it is a good practice due to the slightly better efficiency and also because as the airplane slows down, things just begin happening a bit slower - generally a good thing during an engine out - IMHO.
 
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Can't be a knee-jerk.

The first thing I thought of when I read your story was watching Voodoo recover from an engine failure at Reno last year. I was totally amazed at the amount of altitude the pilot gained by pulling up right away--several thousand feet-- allowing time to troubleshoot, enter the pattern, and come in for a "normal" dead-stick landing on the runway. However, he was also pushing 500 mph when the engine blew! I had an engine quit due to carb ice once while entering the downwind leg in the pattern at cruise speed. I was in perfect position to make a power-off landing on the runway, so there would have been no use pulling up in that situation. I'd have screwed up a normal pattern and hurt my chances for a successful landing. Pulling up while in initial climb-out after takeoff at speeds already close to stall could be deadly. So... I'd say teaching a student to think and react to each situation as it happens is more important than teaching a rigid procedure. Trading airspeed for altitude in cruise flight would probably be a good idea in most airplanes, and should be included in the "bag of tricks" a CFI teaches, but the CFI should be careful that it isn't programmed into the student as an automatic first reaction to engine failure. My 2 cents.
 
Kudos to Kevin

Kevin Horton said:
The lift/drag ratio varies with the angle of attack (AOA). From a pure theoretical point of view, you'll get the absolute maximum glide range if you are at the AOA for best glide the whole time (assuming zero wind). So, if your speed at the time of engine failure is above the speed for best glide, you would want to pull up to increase the AOA to the AOA for best glide. Thus you would climb, trading speed for altitude. You would arrive at the speed for best glide pretty quickly, and then transition into a glide at that speed.

The difference in glide range between the optimum pull up at AOA for best glide, and just holding altitude while the speed bleeds off is probably fairly small, unless the airspeed was very high when the engine failed. In the real world, you have a lot of other things to do to, such as picking a forced landing field, doing the engine failure checklist, declaring the emergency, etc.
Click to expand...
As usual, Kevin gives the answer that makes the most sense! Here are some additional thoughts along those lines.
  • Since there is a (sometimes major) difference between your true best L/D and your engine-out best L/D, you should know both speeds ahead of time.
  • There is also a difference between prop stopped and prop windmilling best speeds. Again, good to know ahead of time.
  • Or, you could use an AOA. I like that better for many reasons.
  • And yes, there may be a time for using minimum sink speed instead of best glide speed. That's very situational. Again, AOA works best.
  • If you are in an RV at cruise, you could easily be 50% or more above the best speed. Blindly zooming up is not so good, but immediately establishing, then holding the correct AOA would get the optimal result.
  • Lastly, the usual rules of thumb are, IMHO, wrong for how to compensate a glide in wind. For illustration, see this. The issue is the change in the drag curve.
 
Another way to look at this: you start with a certain amount of energy, which is the sum of the potential energy (due to your height above ground) and the kinetic energy (due to your speed). You will be losing energy due to the drag. To make the best possible use of the energy you have, you want to be at the speed for best glide. If you are too fast, or too slow, the drag will be higher than it could be, and you will be wasting some of the precious energy.

If you hold altitude until you reach best glide speed, then push over to a glide, you will spend a certain amount of time at a too fast speed, and wasted a certain amount of energy due to drag at the too fast speed. If instead, you pull up and convert some of your speed into altitude, you will spend a much shorter time at a too fast speed, and you will have wasted less energy due to being too fast.

Yes, you will have a bit extra drag as you "turn the corner" during the pull up, as the g will be slightly more than one. But, the opposite occurs when you pushover at the top, as the g will be a bit less than one, which means the drag is decreased during that part of the manoeuvre.

This is certainly an academic discussion for RV flyers, as the difference between an ideal zoom and holding altitude while decelerating would be fairly small unless you were at speeds not seen by RVs.
 
Gravity provides us with only so much energy. What you will get by grabbing altitude is actually going to be a shorter flight path since you will have truncated your flight path by going vertical. In other words, you will have converted some horizontal flight distance into vertical flight distance. Your best option therefore is to stay at altitude and use smooth controlled flight to trim and transition from cruise speed to best glide. Doing so will allow you to cover more ground and might actually be the reason you're able to clear that darn tree!
__________________
Ah, ha. I think that's close. How about; zoom if your landing area is behind you & coast to best glide if your landing area is in front of you. If you don't know where your gonna land, welll.....?
 
Good Discussion

I think this is a really discussion for low time pilots like myself, and a newly built RV-7A. It seems that the logical procedure to the engine out senario depends a lot on what part of the flight you are in. Never the less discussions like this get you thinking about what to do, which sometimes we all get a little complacent on.
 
It Was Instinct

I ran a tank dry by accident once cruising pretty low (1500 AGL) in Illinois. Instinctively pulled back to towards best glide, as I flipped on the boost pump and switched tanks. I ran out of room under the clouds longer before I got to best glide, and was looking for an out when the engine caught.

Hans
 
Rivet, I think that is wrong

The altitude you gain in the zoom will convert into just as much distance in the glide (slightly more actually because of the increased parasitic drag that you are experiencing at the higher airspeed, as Kevin points out). Energy is energy - the same amount will end you up at the same place. You will have slightly less when you get to that place if you let some of it be spent combating a higher parasitic drag than was necessary because you spent slightly longer at a higher speed than best L/D.

Again for practical purposes, the difference is small. In the case of a field behind you, the zoom to climb slows things down and gets you looking at the options sooner (IMHO) rather than concentrating on a smooth and coordinated (efficient) transistion from fast speed to best glide.

Again - it is all technique and what feels comfortable in a stressful situation is important. Whichever technique you chose - practice - practice - practice!!
 
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This is certainly easy enough to test. Mark a 5-20 mile course. At 3000 AGL and 150KIAS pull the power and pitch up for Vglide and descend to 500 agl. Do the same test, but maintain 3kAGL until your speed reaches Vglide. Compare the results. I would think the first technique will be marginally better. Since my son's next flight lesson is on "emergency procedures" we will do this very test.

Of course all of this is meaningless if your engine goes kaput at 500 agl just after takeoff.
 
Rivethead said:
Doing so will allow you to cover more ground and might actually be the reason you're able to clear that darn tree!
Click to expand...


This is assuming you are headed in the right direction in the first place. If your most suitable emergency landing field is behind you, you just traveled farther away from it.

This is an instance where others have said "programming" is not the best option, but to quickly think and determine which option is the best one.

I think if the OP's CFI had said "...immidiatly pitch for best glide and you might gain a couple hundred feet to play with...", then we wouldn't be having this discussion.
 
Most likely your instructor is a surplus military type... I have checked out some ex-jet jocks who did this instinctively when given a simulated engine failure... The problem was they pulled so hard they were almost instantly below Vglide at a ridiculous nose up attitude.......

In a jet fighter, or a Reno Racer using the energy to gain altitude provides a huge pay off in terms of options.... In an RV the payoff would be less depending on what you were doing, but if you were buzzing at Vne and low altitude you could swap airspeed for enough altitude to make some decisions.....

Tailwinds,
Doug Rozendaal
F1 Rocket
 
the plethora of possibilities made my head itch...

but that was the purpose of the original thread. yeah, overall, going to best AOA and maintaining/managing energy most efficiently seem to be best ways to manage in the vertical plane, assuming a lot of speed and altitude in the first place. a couple of responders pointed out too that it's also of great importance to expeditiously get the airplane pointed in the direction of a landing spot, in case restart procedures don't remedy the situation. no single answer for everybody all the time, but thanks all for the discussion, hope it helped others as much as it did me.
 
I agree

with Mickey. And, I certainly would not want to pull back on the stick if I lost an engine on take-off where you may already be flying at or close to best glide. I want to be sure I keep the airplane flying BEFORE I start to check for reasons why it suddenly got quiet.

My two cents
 
My flight student (son) and I went out and tested the power off glide from a low speed cruise to a landing. We started out at about 120KIAS and 6500 DA. Exactly 12nm from the airport I pulled the power and declared, "your engine failed, what are you going to do?" Having primed him, he was quick to pull carb heat (good boy), swap fuel tanks and then pitch for best glide. By the time he started to look for Vglide we had already slowed to below 95KIAS and his cruise trim situation and natural inclinations kept the nose up slightly and within seconds we were descending at Vglide. I had him flow across the switches and gauges, tune to 121.5 and Milwaukee approach and simulate 7700. At first I didn't think we were going to make the airport, at 12 nm it seem a little far. We had a cross wind at altitude and I don't recall that it changed much in the descent (according to EFIS). We had no trouble making the airport and were able to get to the far-side downwind at 1500msl. I figure with a wind-milling prop we had about a 10:1 glide ratio. In our situation I don't think having him pitch up for additional altitude would have gained us much. Perhaps more of a distraction than anything.

I suppose if you were down low and had excess speed it would be a good idea to pull back and bleed off the speed and gain a few feet. Still, your main concern should be landing the plane and possibly getting the engine restarted. One thing for sure, Vglide might give you maximum distance, but if you read the NTSB reports many accidents involving dead stick landings result in the pilot over-shooting a perfectly good land spot. Putting yourself in a Key familiar landing position (I.E. abeam the touch down spot (mid-field) on downwind) should be primary and everything else secondary. CFI's will tell you that many students will spend several minutes fiddling with the plane while they fly further and further from a landing spot. By the time they start to circle or get set up for the downwind, were miles away. I don't think there is a right or wrong answer in this situation. Just SAVE YOUR BACON, AVIATE, NAVIGATE AND COMMUNICATE!
 
apkp777 said:
I figure with a wind-milling prop we had about a 10:1 glide ratio. In our situation I don't think having him pitch up for additional altitude would have gained us much. Perhaps more of a distraction than anything.
Click to expand...

I would agree with you...in this particular situation.
As already pointed out in many other posts, the best training is to learn to quickly analyze the situation and and make the best choice based on that.
Since this is an RV forum...if we broaden the possible context to a situation more likely if you are flying an RV cross country.... Lets assume you and your son were 35 miles east of UAO, on your way to visit Van's Aircraft (instead of over the mostly flat land of Wisconsin). Since most RV's are capable of true airspeeds in cruise of 160 - 170 kts, we will assume you are going at least that fast. Add to the situation that you are on a decent (we will pretend it is smooth air) so you may be at a true airspeed closer to 170 -185 kts.
So, there you are, excited to get to Van's and you have a sudden engine failure. The terrain you will be over is not full of choices for a forced landing, but there is some out there if you can find them and then reach them. Pulling up it that speed might give you another 2 minutes (or even more) worth of glide time or just enough glide distance to reach an otherwise unreachable landing area.

Bottom line...continuing flight in the direction you are already going while dissipating excess airspeed, is only a good choice if you know that it is the best direction to go for a safe landing (as in you already pointed towards an airport that you think you can reach).

I know some will say that you should always be looking and have a forced landing spot in mind. I agree and I try and always fly this way.
In this imaginary case, you are actually crossing a mountain range (the Cascades) that you could remain high enough to almost glade to the valleys on either side if need. It would not be very practical though because that would put you over Vans home airport with about 7000 ft of altitude to loose. Some pilots might choose to do this , most probably do not. The reality is, when flying over the mountains there can be periods of time when there is no apparent emergency landing area (unless you choose to always follow an interstate hwy...that's another whole discussion in it self). There are times that gaining just another 1500 feet or so might bring into view a landing choice that would otherwise be missed.

As already emphasized...learn to analyze the situation and make a quick decision based on that. Then stick with the decision. But above all else.. Fly the airplane
 
don.olandese said:
Practicing/de-rusting the other day in a spam can, instructor wanted me to - upon simulating sudden complete loss of power in cruise - immediately raise the nose to gain a hundred or two feet of altitude - i.e., zoom up to maximize altitude - before initiating the rest of the emergency procedures (check stuff, establish proper pitch and glide speed, etc). I suspect that gaining the altitude at engine-failure is less beneficial than simply allowing the airspeed to bleed off gradually, THEN pitching to proper best-glide etc. i think that because the induced drag during a sudden climb should be comparatively greater than during a gradual deceleration. The POH just says "establish pitch attitude for best glide:" no details on whether to slow the airplane with a climb or let it slow down gradually in level flight, which is how i've been doing it for years. Comments, references, wild-*** opinions? whatever is the right answer probably applies to a lot of different airplanes, including our favorites...
Click to expand...

I have a fairly detailed answer for you, if you'll bear with me. I should first say that I teach a class in optimal control theory, which is the discipline that addresses questions exactly like this. Quite some time ago, I did the calculation for the best result, and the answer is interesting, I think. As a disclaimer, I should say that I'm not sure that it makes sense from an operational point of view, but I can say something about the optimal solution from a theoretical point of view.

With that said, it turns out that the way to maximize glide is to immediately retrim the aircraft for best glide speed, and then allow the plane to naturally achieve a new equilibrium, but to add some damping (damping ratio of about 0.7) to the resulting phugoid mode. In practice, that would mean a pretty firm zoom up, settling quickly into a stable glide. For example, if you are cruising at 180, and best glide is 90, the result above would actually imply a 4g pullup, which of course would be impractical in a normal category aircraft.

Now, there's some shortcomings to the analysis, and I could do a more refined analysis with the tools I have now, but it won't change the basic result, which is that if you are flying well above Vglide, it probably is worth zooming up. If nothing else, you'll get the aircraft established at the glide speed faster, and at a higher altitude, leaving more time to do other urgent tasks.
 
Thanks Steve

Regarding the most efficient method - This is what I suspected and what several have hinted at in this thread. Thanks for the technical confirmation that it is true.

But maybe most important is your last point - doing things in an orderly fashion, getting it done quickly, and moving on to the next critical task is very important. Establish the best glide - zoom up or nose down-whatever gets it done NOW!! and on to the next most urgent thing - FINDING A FIELD - then clean up the cockpit (restart or secure whichever time allows) - then concentrate on aviating efficiently.

Having done this many times (simulated engine failures) from all kinds of altitudes and airspeeds, as both a student, instructor and solo practicing - the most common error (or screwed up decision point) is finding and COMMITING to a field.

Anything that gets to that decision most efficiently is better. And the first thing that has to be done in that thought chain is transitioning the aircraft to best glide - get it done quickly and efficiently and then get on with the next step - bang bang bang.

Enough soapbox. Hope it helps someone.
 
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Swapping airspeed for altitude

Here's a great illustration of swapping airspeed for altitude. Some of the youtube videos called it incorrectly a F-16, but it was the BAE CT-155 Hawk, flying closed pattern at Moose Jaw, S.K.

Short version,
Two seat jet trainer, climb out from touch and go, bird strike at 239 knots while 70 feet AGL. A 1/2 pound gull took out the AOA probe and the engine. Zoom climb to about 1,610 feet AGL (kinetic energy plus maybe some thrust- don't know for sure).

The vidio is a real nail biter, both pilots survived, though the instructor received serious injuries. If the link doesn't work use, hawk crash 2004 as keywords.

http://www.youtube.com/watch?v=Z00gU-OQdQI&NR=1

There was a Flight Safety Investigation of the accident. Section 2.4 is a discussion of pilot response. They had different procedures based on speed, altitude, and what the malfunction was. Reading through the expected procedures, (as someone with 0 jet time) it definitely sounds like a lot to sort out when the engine isn't isn't performing and the ground is close. Of course our RVs are a different animal, nevertheless, the take away for me was it is important to be cognizant of what phase of flight I'm in, have a plan, and the better I understand my engine and airframe, the more likely I am to make good choices.
Investigative report- file # 1010-CT155202 http://www.check-six.com/images/MooseJaw/ct155202-eng.pdf
 
one maneuver better than two

In any such crisis you need to conserve resources and keep things simple.

Pitching for best glide and holding it is just one, simple maneuver which can be quickly executed. It may also give better endurance and glide range than other options.

Decelerating and then establishing a glide is at least two maneuvers which take longer than the above and demands more action and attention by the pilot at a time of high workload.

Pitching for best glide does not mean zooming or going to vy as quickly as possible.

Pitch for best glide!
 
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