Single engine normal climbout: Vx or Vy?
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You are not paying attention
If straight out departure, there is no "safe return altitude". In your question, you didn't specify 5,000 feet remaining at OEI. If you take-off into the wind, if there is one, you can't "turn into the wind" with any Bank after OEI. You acknowledge that there is no glide distance as great or greater than distance from runway at OEI, yet you say you've practiced it many times. I hope you are at altitude when practicing this, not near the airfield, reading the Altimeter correctly, and solo.
AF
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Your post is a little confusing to be honest.. of course you can't turn into the wind if you have a straight head wind, that is obvious. Turning into the wind only applies if you have any crosswind. And most often, there will be a slight crosswind from either direction.
About the glide distance, I have not made any calculations or anything to prove/disprove anything when it comes to that. The only thing I know is that if I lose my engine in a C-172 on a standard day I will be able to make it back if I lose my engine at 600 feet. Because I have practiced it before many times. It is certainly not a problem at all, and as I said, when I know I can make it back to the runway, why should I land straight ahead in stead?
About the glide distance, I have not made any calculations or anything to prove/disprove anything when it comes to that. The only thing I know is that if I lose my engine in a C-172 on a standard day I will be able to make it back if I lose my engine at 600 feet. Because I have practiced it before many times. It is certainly not a problem at all, and as I said, when I know I can make it back to the runway, why should I land straight ahead in stead?
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Sean
Once you are brakes off and rolling in this a/c, you are committed to landing straight ahead, whether on RW or beyond. You continue to say 600 feet is a "safe return" altitude, but you neglect to mention the distance from the departure end. It is my contention through experience and training (albeit 40 years ago) that by the time you reach 600 feet at any airspeed, you are not able to turn and land back on the airstrip of departure. I hope that isn't confusing, but if I am the only one who gets it, I'll be the one safely on the ground (hopefully) while others are rolled into a ball or on fire. (IMO).
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Have you tried before? I guess not.
Well I have, and guess what, I made it back to the runway every time from what I determined to be safe turn back altitude. Did you not read what I said?
Arguing against it is just stupid. I am telling you I have done it before several times. But please be my guest, if you choose to rather land in a tree that's fine. If I know I'll make it back then one thing is for sure: I'm landing on that damn runway.
As a side note we had an incident here at the airport where I work just a week ago. A pilot flying solo in a light sport airplane had an engine failure 400 feet on take off. Guess what. He turned back and landed more than half way down the opposite runway from where he departed. That being said I would never make the turn in the 172 from 400 feet (too low to make the turn itself), but this guy made the decision and made it back safely. Better than hitting the city packed with power lines and buildings straight ahead? Oh yes.
Well I have, and guess what, I made it back to the runway every time from what I determined to be safe turn back altitude. Did you not read what I said?
Arguing against it is just stupid. I am telling you I have done it before several times. But please be my guest, if you choose to rather land in a tree that's fine. If I know I'll make it back then one thing is for sure: I'm landing on that damn runway.
As a side note we had an incident here at the airport where I work just a week ago. A pilot flying solo in a light sport airplane had an engine failure 400 feet on take off. Guess what. He turned back and landed more than half way down the opposite runway from where he departed. That being said I would never make the turn in the 172 from 400 feet (too low to make the turn itself), but this guy made the decision and made it back safely. Better than hitting the city packed with power lines and buildings straight ahead? Oh yes.
What did you mean by this bookworm? That in these airplanes that you describe C/L max is the best glide speed, C/L max is Vx, or both like FE hoppy said?
C/L max, by which I now presume was meant maximum lift coefficient (CLmax), has nothing to do with best angles or rates of climb, unless the stall is limiting angle of climb, which is unusual in a prop and even more unusual in a jet.
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I misread it as L/D max, which is equivalent to best angle of glide in all aircraft, and best angle of climb in a constant thrust aircraft (ideal jet).
C/L max, by which I now presume was meant maximum lift coefficient (CLmax), has nothing to do with best angles or rates of climb, unless the stall is limiting angle of climb, which is unusual in a prop and even more unusual in a jet.
C/L max, by which I now presume was meant maximum lift coefficient (CLmax), has nothing to do with best angles or rates of climb, unless the stall is limiting angle of climb, which is unusual in a prop and even more unusual in a jet.
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Now that we're talking about it and kind of off topic already, would any of you mind explaining why L/D max = Vx in jets but not prop airplanes?
Would very much appreciate that!
Would very much appreciate that!
Because at that point in a piston [a constant power variable thrust machine--as Bookworm explained] you have the lowest drag coincident greatest possible lift coincident the only thing affecting climb rate as such is the difference between POWER required and POWER available, however as the power falls off with altitude while drag is always equal to thrust....
But, ROC will decrease so to maintain the highest possible ROC [the condition required of Vx] at less power [from critical altitude] an increase in the lift term and therefore angle of attack is required this action induces drag and requires greater thrust maintain that new AOA at a constant altitude,...i.e there's less actual drag at altitude, but more drag required because more lift is required, so more thrust is required,...READ CAREFULLY THIS!!!
And, since power is thrust X Vtas and increase in velocity is required to maintain the required power for max climb angle,...
so in pistons Vx continually increases until it converges with Vy at the absolute performance altitude, whereas a jet produces constant thrust and a constant the AOA is that which produces the greatest climb rate i.e the AOA for L/Dmax
Oh yeah listen to Airfoilmod, he's cool and your procedure may kill you land straight ahead with only shallow turns to avoid obstacles,..as most flight handbooks advise
PA
But, ROC will decrease so to maintain the highest possible ROC [the condition required of Vx] at less power [from critical altitude] an increase in the lift term and therefore angle of attack is required this action induces drag and requires greater thrust maintain that new AOA at a constant altitude,...i.e there's less actual drag at altitude, but more drag required because more lift is required, so more thrust is required,...READ CAREFULLY THIS!!!
And, since power is thrust X Vtas and increase in velocity is required to maintain the required power for max climb angle,...
so in pistons Vx continually increases until it converges with Vy at the absolute performance altitude, whereas a jet produces constant thrust and a constant the AOA is that which produces the greatest climb rate i.e the AOA for L/Dmax
Oh yeah listen to Airfoilmod, he's cool and your procedure may kill you land straight ahead with only shallow turns to avoid obstacles,..as most flight handbooks advise
PA
Last edited by Pugilistic Animus; 20th Apr 2009 at 18:17. Reason: bold
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Thanks PA, appreciate your explanation 
In their own books, the FAA generally explains the hazards of attempting to turn back to the runway if you have an engine failure on take off. However, they also say this:
Quote FAA-H-8083-3A, Airplane Flying Handbook
As I said, it is all about knowing your airplane. Some will do it and some will not.
In their own books, the FAA generally explains the hazards of attempting to turn back to the runway if you have an engine failure on take off. However, they also say this:
Quote FAA-H-8083-3A, Airplane Flying Handbook
Concerning the subject of turning back to the runway following an engine failure on takeoff, the pilot should determine the minimum altitude an attempt of such a maneuver should be made in a particular airplane.
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I'm not sure exactly what you meant by that, but here is the rest of the sentence you quoted:
Concerning the subject of turning back to the runway following an engine failure on takeoff
SeanCG,...
no they definitely mean a 360 ---takeoff ends at 50' agl so the mean departure climb,...and many runways are off of virtual cliffs,..since the airplane flying handbook,..I have it [both of them],..borrows [steals] from many sources,...such as handling the big jets or aerodynamics for naval aviators,...sometimes the wording gets ambiguous,...but one of the best references available for non-engineer pilots
P.S. I only quoted the part of the sentence I needed
but an inquisitive nature such as yours is good in this business ---just be careful brother!!!
PA
no they definitely mean a 360 ---takeoff ends at 50' agl so the mean departure climb,...and many runways are off of virtual cliffs,..since the airplane flying handbook,..I have it [both of them
],..borrows [steals] from many sources,...such as handling the big jets or aerodynamics for naval aviators,...sometimes the wording gets ambiguous,...but one of the best references available for non-engineer pilotsP.S. I only quoted the part of the sentence I needed
but an inquisitive nature such as yours is good in this business ---just be careful brother!!!
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Piper Arrow
In airplanes that don't glide too well (like our school's piper arrow) there is no safe altitude.
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Pick up your AFH PA, and you will see that the context is definitely an engine failure shortly after take off on the departure leg. You will see it clearly, there are three big paragraphs concerning the turn back ! But oh well. I promise I will not kill myself doing these things
sapperkenno, I guess it's the weight and short stubby wings which makes it hard to turn back in that airplane.. I was at least unable to do it, it sinks way too fast. Perhaps it would be possible from like 800-1000 feet with a strong headwind on departure, but who knows. I would not risk turning back in that one, that is for sure!
sapperkenno, I guess it's the weight and short stubby wings which makes it hard to turn back in that airplane.. I was at least unable to do it, it sinks way too fast. Perhaps it would be possible from like 800-1000 feet with a strong headwind on departure, but who knows. I would not risk turning back in that one, that is for sure!
Sean,
I hope like hell you are not teaching or thinking "a safe altitude to turn back in a C172 is xxxx feet".
If you are trying this out in flight then you are planning for it without including startle factor, reaction time etc so the testing you are doing to find out that altitude is not valid for a real world engine failure. Loss of about 200 feet prior to putting a plan into action is about what I see with my students when they are not expecting an EFATO.
There are far to many variables to make bold statements. What works at a sea level airfield will not work at a 3000 AMSL airfield or an airfield with 3000 feet PA or DA. A MAUW C172M would be lucky to do 300 fpm at a 3000 foot PA airport and that will put you a long way up wind before your magic altitude.
Trying to land back at a 2000 meter long will give you a false sense of confidence. What about landing back on a 400 meter airport?
What will the ground speed be on the attempt to return? What would be your limit? What radius of turn do you need to return to the runway? What is the aircrafts limit? How much energy will you have to dissapate before you go through an immovable object (runway end fence for example) and survive?
What about the aircraft taking off just behind you, how big is it and can it move quickly out of your way, how skilled is that pilot, and does he see what you are up to?
Is there a steep wind gradient on takeoff, or sink at the departure end?
A MTOW C172 will probably not make it to the airfield (nil wind) from the altitudes you are quoting. (If you insist on being a test pilot and to try it please do not load Pax to increase the weight).
Back to your question Vx or Vy.
Answer - It depends on the conditions on the day and the airport you are flying from.
When you look at all the variables the safe way is to land straight ahead into wind or there abouts, and hit the softest thing you can find (aircraft are easy to replace). Yes at some point a return to the runway may be possible but are you willing to BET YOUR LIFE and YOUR PASSENGERS LIFE that you have the skill and the luck to make it?
Finally thanks for bringing up the topic, great discussion so far.
I hope like hell you are not teaching or thinking "a safe altitude to turn back in a C172 is xxxx feet".
If you are trying this out in flight then you are planning for it without including startle factor, reaction time etc so the testing you are doing to find out that altitude is not valid for a real world engine failure. Loss of about 200 feet prior to putting a plan into action is about what I see with my students when they are not expecting an EFATO.
There are far to many variables to make bold statements. What works at a sea level airfield will not work at a 3000 AMSL airfield or an airfield with 3000 feet PA or DA. A MAUW C172M would be lucky to do 300 fpm at a 3000 foot PA airport and that will put you a long way up wind before your magic altitude.
Trying to land back at a 2000 meter long will give you a false sense of confidence. What about landing back on a 400 meter airport?
What will the ground speed be on the attempt to return? What would be your limit? What radius of turn do you need to return to the runway? What is the aircrafts limit? How much energy will you have to dissapate before you go through an immovable object (runway end fence for example) and survive?
What about the aircraft taking off just behind you, how big is it and can it move quickly out of your way, how skilled is that pilot, and does he see what you are up to?
Is there a steep wind gradient on takeoff, or sink at the departure end?
A MTOW C172 will probably not make it to the airfield (nil wind) from the altitudes you are quoting. (If you insist on being a test pilot and to try it please do not load Pax to increase the weight).
Back to your question Vx or Vy.
Answer - It depends on the conditions on the day and the airport you are flying from.
When you look at all the variables the safe way is to land straight ahead into wind or there abouts, and hit the softest thing you can find (aircraft are easy to replace). Yes at some point a return to the runway may be possible but are you willing to BET YOUR LIFE and YOUR PASSENGERS LIFE that you have the skill and the luck to make it?
Finally thanks for bringing up the topic, great discussion so far.
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Good post C100driver, thank you.
I agree mostly with everything you say. But do not get me wrong, if you re-read my posts in this thread you will see that I have never mentioned any specific altitude, and I have always said that it varies with atmospheric conditions etc. etc..
This is definitely a maneuver one must train for to be able to accomplish, and one must of course be aware of all the factors you mention to make the safe decision of turning back to the runway if that is possible. This is always also why I was taught to always do an emergency briefing prior to departure to go through all this before hand mentally and decide whether conditions would favor turning back or not etc. etc...In the end as I have mentioned countless times it's all about knowing what you and your airplane are capable of doing. If ever any doubt, landing straight ahead is the best option. However, as I once again already have said, if I know for sure that I can make it (partially because I have done it before), I won't hesitate.
Good training pays off, and one day it might save my life or save me from injury.
I am curious to know which conditions you think will favor Vx over Vy in this situation, if you do not mind sharing ?
I agree mostly with everything you say. But do not get me wrong, if you re-read my posts in this thread you will see that I have never mentioned any specific altitude, and I have always said that it varies with atmospheric conditions etc. etc..
This is definitely a maneuver one must train for to be able to accomplish, and one must of course be aware of all the factors you mention to make the safe decision of turning back to the runway if that is possible. This is always also why I was taught to always do an emergency briefing prior to departure to go through all this before hand mentally and decide whether conditions would favor turning back or not etc. etc...In the end as I have mentioned countless times it's all about knowing what you and your airplane are capable of doing. If ever any doubt, landing straight ahead is the best option. However, as I once again already have said, if I know for sure that I can make it (partially because I have done it before), I won't hesitate.
Good training pays off, and one day it might save my life or save me from injury.
Back to your question Vx or Vy.
Answer - It depends on the conditions on the day and the airport you are flying from.
Answer - It depends on the conditions on the day and the airport you are flying from.
Three that I regularly operate from I use Vx unless Vy is the best choice for the conditions on the day. ie turbulence, windshear etc I don't use Vx in heavy 200 series cessna as they are not as forgiving as the 100 series when the engine stops. Piper Slab wings I always land ahead as the world can always do without one more Cheroclunk 
1 Takeoff from one airfield that departs over a nasty piece of open sea - making it back to land or very close to shore is the priority, returning to the strip is not possible however a clear area is along the coastline. Height v Distance
2 Takeoff uphill toward gently rising terrain. Ground rising under aircraft.
3 Short (300 meter) bush surrounded strip with a safe crash landing at the strip or in a river valley behind and to the side of the strip.
They are probably extreme cases but are examples were a different thought process than simple "must do this" rule apply.
One other that I can think of would be an extra long strip where a straight ahead landing is possible. (not the best one I could think of but another reason Vx could be better than Vy in that situation)
1 Takeoff from one airfield that departs over a nasty piece of open sea - making it back to land or very close to shore is the priority, returning to the strip is not possible however a clear area is along the coastline. Height v Distance
2 Takeoff uphill toward gently rising terrain. Ground rising under aircraft.
3 Short (300 meter) bush surrounded strip with a safe crash landing at the strip or in a river valley behind and to the side of the strip.
They are probably extreme cases but are examples were a different thought process than simple "must do this" rule apply.
One other that I can think of would be an extra long strip where a straight ahead landing is possible. (not the best one I could think of but another reason Vx could be better than Vy in that situation)
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Landing straight ahead into any water is far better than stalling, crashing and burning trying to make it back to the airport.
Compare the outcome of the following two engine failures in PA-32 aircraft:
200204328
vs
200802048
In the first turnback attempted - literally crashed and burned and six people died.
In the second ditching accepted - five? people bobbed around in the ocean for a short period of time before being rescued.
Yes - turnbacks are possible in a high performance aircraft - it is a standard procedure for ASEPTA approved aircraft (IFR charter flights in single engine turbine aircraft) - and ASEPTA pilots are trained in the procedure.
Many people have died attempting turnbacks in piston singles - particularly when the aircraft is loaded - most people try it empty or with just an instructor on board. Whilst the glide angle doesn't change with extra load, the gradient achieved during climb certainly does. Add in high temperatures, high humidity (affects piston engine performance significantly) and high altitudes and the probability of getting back to the field reduces dramatically.
Also consider the energy equation with 15 knots headwind on takeoff and a touchdown speed of 45 knots:
Land straight ahead and the touchdown ground speed will be 30 knots.
Land in the opposite direction and the touchdown ground speed will be 60 knots.
Energy is proportional to the square of velocity - double the velocity equals four times the energy.
I don't know about you, but if the plan doesn't go perfectly I'd much rather have a quarter of the energy at the crash site.
If you are an instructor and recommending turn backs I hope you have excellent professional indemnity insurance - because if someone stuffs it up and the pilot survives and says 'my instructor told me to' the lawyers for the passengers or their estates will be rubbing their hands with glee.
Compare the outcome of the following two engine failures in PA-32 aircraft:
200204328
vs
200802048
In the first turnback attempted - literally crashed and burned and six people died.
In the second ditching accepted - five? people bobbed around in the ocean for a short period of time before being rescued.
Yes - turnbacks are possible in a high performance aircraft - it is a standard procedure for ASEPTA approved aircraft (IFR charter flights in single engine turbine aircraft) - and ASEPTA pilots are trained in the procedure.
Many people have died attempting turnbacks in piston singles - particularly when the aircraft is loaded - most people try it empty or with just an instructor on board. Whilst the glide angle doesn't change with extra load, the gradient achieved during climb certainly does. Add in high temperatures, high humidity (affects piston engine performance significantly) and high altitudes and the probability of getting back to the field reduces dramatically.
Also consider the energy equation with 15 knots headwind on takeoff and a touchdown speed of 45 knots:
Land straight ahead and the touchdown ground speed will be 30 knots.
Land in the opposite direction and the touchdown ground speed will be 60 knots.
Energy is proportional to the square of velocity - double the velocity equals four times the energy.
I don't know about you, but if the plan doesn't go perfectly I'd much rather have a quarter of the energy at the crash site.
If you are an instructor and recommending turn backs I hope you have excellent professional indemnity insurance - because if someone stuffs it up and the pilot survives and says 'my instructor told me to' the lawyers for the passengers or their estates will be rubbing their hands with glee.