Peter wrote:
I cannot work out the above post. At least there is a lot of puctuation missing.
That’s because you speak proper English 
For us non-natives everything is clear we speak like that or worse
If Vx is required, maybe the planned departure is a not good idea at all.
In most SEP, at sea level max performance you are looking for 1:6 with Vx vs 1:8 with Vy (better numbers can be derived from POH as max ROC/VX vs max ROC/Vy assuming ROC remains same on both), on hot days, you are looking at 1:10-1:15 for both
Definitely, not a good idea to play 1:7
Though not a standardized training method, for one particularly obstructed runway I used to operate from (1400’ to 75’ high trees) my habit was to aim for 2/3 up the trees as though I planned to take the trees out with the plane. Happily, self preservation and a reasonable sense of fear had me pull up at the last moment, and clearing the trees was never a problem. And when I did, I had a nice reserve of speed. Picking a leaf out of a mainwheel is less a problem than picking the whole plane out of the forest!
Speed is your friend. Once you have enough, altitude is a friend too. Unless you’re flying aerobatics, having altitude is of little benefit without also having speed.
Pilot_DAR wrote:
Climb airplanes at Vy or faster, unless there is an obstacle to clear on takeoff. In that case, get the airplane safely airborne, climb at Vx until you clear the obstacle then accelerate to Vy or more, and climb away safely. Why attempt anything different?
I agree. That makes a lot of sense for all the quoted reasons.
There is another thing from a performance point of view. The “total distance” calculation in the POH’s are clearly calculated using Vx to 50 ft above ground. Accelerating before that will mean you will not reach book values for the total distance as given in the POH.
Clearly this is not a big deal if a) there is runway longer than total distance plus a generous reserve, b) if there is no obstacle and c) most importantly you are aware of this and take it into account.
On short runways, it often happens that total distance is greater than the actual runway lenght while ground roll is obviously well within the runway lenght. In this case, it has happened a number of times that people start panicking when the runway end disappears under them before they reach 50 ft AGL or what seems a “safe height” from a view point. They start pulling and stall and crash, those who survive afterwards claim “the airplane did not climb!” . Well, it did but quite shallow because of low speed and high AOA. There Vx is not only the best angle but also minimum speed!
So Vx does have it’s uses, no question about it, but clearly from a safety point of view should only be used if conditions mandate it. As for EFATO, only training can help.
Flying min drag speed (Vy) does allow one to clear obstacles as Total Energy = Height + Speed is at it’s maximum
The only way to clear the trees is to aim at them, there are no other ways worst case you know you will hit them from 300 yards with plenty of energy to manoeuvre, this is different from stalling straight into them at Vx, also the climb gradient is usually at 1% when one is few kts bellow Vx on underpowered types, so climbing faster offer better protection when ASI wiggles around Vx
When engine quits Vx goes to the bin while Vy is usually near Vbg…people teach Vx in PPL textbooks as it’s a nice concept to fill someone’s V-speed card in SEP, the same people teach 25/25 in Arrow with max mixture instead of wide open throttle, max rpm and leaning…go figure !
Climb airplanes at Vy or faster, unless there is an obstacle to clear on takeoff. In that case, get the airplane safely airborne, climb at Vx until you clear the obstacle then accelerate to Vy or more, and climb away safely. Why attempt anything different?
Because climbing at Vx is aerodynamically inefficient.
It may be more efficient with respect to engine power wasted on aerodynamic drag to gain excess kinetic energy (speed in excess of Vx) in ground effect and then, at the last second, to trade that stored excess KE for potential energy to clear the obstacle. But that needs a bit of practice and may be airframe dependent.
Peter wrote:
There is a great article in the last US AOPA magazine by Barry Schiff, making the point that if you get an engine failure during a Vx climb, it is very likely to kill you, because at that point you basically have no options left.
I have been training this for years, including last week in a C185 amphibian. This is horribly totally omitted during any formal fixed wing pilot training I’m aware of. In helicopter training, it’s required training. Indeed, one helicopter I have flown actually has a yellow band on the VSI. I asked my mentor why the yellow band was there. He explained that the helicopter could be, though should not be, climbed at such a high rate, that it would be going up so fast that in the case of an engine failure it would be unsafe to attempt to transition to an autorotation. Many airplanes can do this – and no one seems to know, much less train anyone else about it!
If you climb an airplane more slowly than Vy, it is certain that there will be a particular altitude range within which recovery to a successful gliding landing will be difficult or impossible following an engine failure. That altitude range will vary by the airplane type, and how much slower you are than Yv. When I trained this in the Decathlon earlier this year, that altitude band was happily small, I suspect less than 50 feet based upon the training I did for my colleague. When I demonstrated it in the 185 amphib the other week, I showed it’s at least 200 feet.
Sadly, if you went to your local flying school/instructor and asked for specific training on this, you might be met with a scoff, or a puzzled delayed response – but not an explanation! The obverse being those very silly pilots at “STOL” competitions, who appear to climb hundreds of feet up after a short takeoff, just hanging on the propeller – fools! Don’t they know that “STOL” stands for Short Takeoff and Landing, and has nothing whatever to do with steep climb out! Sure, get the airplane off the surface in an amazingly short ground run, and impress your buddies Then lower the nose, accelerate to a safe speed, and climb away safely, with speed in your back pocket in case the engine quits on climb out.
Climb airplanes at Vy or faster, unless there is an obstacle to clear on takeoff. In that case, get the airplane safely airborne, climb at Vx until you clear the obstacle then accelerate to Vy or more, and climb away safely. Why attempt anything different?
if you get an engine failure during a Vx climb, it is very likely to kill you
Very likely true at low altitudes, depending on type and flap setting. Then at higher altitudes there is rarely any use for Vx, with imminent CFIT being the only exception I can think of right away.
And that is why I have always teached Vx as an non-normal procedure. If Vx is required, maybe the planned departure is a not good idea at all.
gallois wrote:
Yes, if there is an engine failure when climbing at Vx it is likely to kill you because you will more than likely hit the obstacle you are trying to avoid by climbing at Vx.
Of course – but the situation may not be that different from a normal take-off where an engine failure may also kill you, depending on what that obstacles we’re talking about.
Yes, if there is an engine failure when climbing at Vx it is likely to kill you because you will more than likely hit the obstacle you are trying to avoid by climbing at Vx.
