Point Of No Return

[John.com]

Thanks to you Peter I have just made some very meaningful changes to my Pre-Engine Start W&B Checklist!!

Any comments . . . . as this checklist is now work-in-progress!

e.g. Any suggestions on minimum needed for "Runway Remaining for Aborted Take-Off"? Say at 45mph?

Safe Skies

John

[Mogas]

Thats a good honest post Peters, thanks for sharing and I hope that some will take away a valuable lesson from it.
The go or no-go decision point in the takeoff roll you refer to is known as V1 amongst the big blik pilots, it is calculated for every takeoff and takes into account engine performance dependant on density altitude, runway slope/length and takeoff weight.
The non flying pilot will call "V1" when the calculated speed is reached on the takeoff roll and it comes before the VR or rotate call. The reason it is called is so that if the sh1t hits the fan a quick decision can be made to go or abort.
Takeoff accidents are more often than not much more dangerous than landing accidents, this is because of the speed and inertia involved.
It is not practical for us as light aircraft pilots to accurately work out V1 for our takeoffs for every flight, proper graphs and accurate weights and temperature data are needed.
However, your experience will have shown you that you were right on the limit that time and there in lies that valuable lesson.
If ever your gut tells you again that it is going to be tight, pay attention. Work out a decision point for yourself, a spot alongside that runway that you will see will do. This spot will provide enough abort distance should you need it. If you have not reached takeoff speed before your spot, abort without wasting any time.
It is a good idea to be well on the conservative side when in comes down to deciding on a decision point.
Mogas

[Asterix]

Pieta het geskryf: (My highlights:)

"Back to the story…on the threshold ready for take-off the wind drops. I calculate, no wind, heavy laden I should lift off there. Thoughts flood my mind. Shall I hold the brake put full throttle leave the brake as in short field take-off etc. I decide not to but ease the throttle into full power. Move off is slow and I become anxious. I see we have reached 45mph and a slight lift is felt. Suddenly were airborne but we all over the place as I ease the bar in we almost touch down but climbing slowly. Valuable seconds pass and this is where I feel that I made my mistake.

The speed the aircraft is now too fast and too high to ever touch down and stop safely on the rest of the runway, veld and the fence for the sudden stop. This was my point of no return. Here when I should have continued to fly like a bat out of hell I eased back on the throttle in an attempt to abort suddenly a gust of wind (crosswind) or (Guardian Angel)points me into the crosswind leg and we have all the altitude we need to clear all obstacles and foot in die hoek we continue crosswind into the downwind leg with a steady climb out of the circuit into the GF to 6000 foot. You know how nice it is up at 6000 foot? I will treasure that awesome feeling for ever."

Hi Pieta. The way I see it, you were heavy,(not necessarily overweight) and you got airborne just above stall speed. As you eased the bar in, the weight of your aircraft overcame the lift, and it felt as if you were gonna fly into the ground. Plus, you had NO headwind, out of air, making it even harder for your wing to fly. This has happened to me, heavily laden with fuel and gear on a cross country.

This was then followed by easing back on the power, which made it even worse, and your wings were on the stall, due to reduction in airspeed and thrust, in an already kak situation. And maybe a wing dipped because you fought the weather-cocking too hard?

IMHO: (luckily me and Pieta are friends, so he will take my view in good spirit:)

You aborted too late, if you wanted to abort. Once airborne, the point of no return is way behind you. You then panicked because you saw that you are not getting lift, and came back on the power. Plus the trike was trying to fly into the crosswind, which took you of your direction over the runway, and you tried to keep it straight. THERE was your two mistakes. Remember: "When in doubt - rev it out." Remaining full power with a balance on the bar between airspeed and lift, would have been your best option. This is what happened towards the end of your account, where you put "voet in die hoek", the wing weather-cocked into the crosswind, and suddenly you had lift. Remember on a crosswind take-off - your wing apex WANTS to point into the wind. In my opinion - let it do that - while still remaining over the runway as best as you can. Best way to get good lift. And once airborne - keep the power!

Thanks for sharing my friend - and this is only my humble opinion!

[Gyronaut]

Valuable lesson, thanks for sharing it with us Pieta.

It reminds me of something that happened while teaching a high time ATP to fly a Gyro. He was already solo and we were planning on going on a nice long cross country so he could familiarise himself with the GF's in the area. Full tanks, I weigh 78kg, he's about 100kg, we're at sea level so we rarely bother to do the calculations since we're flying in air as thick as soup and we're way below the MAUW for this altitude. It was a windless hot and humid day. Shouldn't be a problem.

3/4 of the way down the runway we reach my mental cut off point and we are barely airborne with no positive rate of climb evident. I shout that I have control, cut the power and land hitting the brakes. We barely manage to come to a stop with the nose wheel off the end of the runway on the sand. He looks at me in horror and admits that the absence of V1 and VR readouts by his first officer had lulled him into such a sense of security that he would have kept the power on regardless and ended up flying straight into the trees at the end of the runway had I not been on board with him that day.

I realised that I had neglected to stress the importance of DA and MAUW calcs (He is a Comm ATP with thousands of hours after all and it goes without saying in my mind). Different aircraft, different circumstances and different limits to what he was accustomed to could easily have ended tragically.

Thankfully he later stated that this one aborted takeoff was as valuable as 10 hours of training and that he would never allow himself to fall into that particular trap again.

As an instructor I learned a lot from this incident and now always stress the importance of DA and MAUW calcs in addition to the fact that moisture displaces air and does not generate lift. (regardless of whether I consider the pilot/student a sky-god or not). I have also since moved my personal go/no-go point on this runway 30 meters closer than it was before.

I have also found that passengers (male and female) often fib about their real weight and agree that they will tell you their 'percieved' weight - so add a couple of KG's to whatever they tell you to err on the safe side.

Fly safe and I am thankful that Pieta and his pax made it safely. We'll all benefit from his experience.

Len

[Thatchman]

We have a very short runway and almost always when 2 up with full fuel VR is always after V1.

An important tip when you are heavy is to keep it on the ground a bit longer. This seems a bit daunting with the end of the runway looming but this way when you rotate then the plane wants to fly.

Nothing worse when to rotate at marginal speed, bar forward and the plane is wallowing around. Its difficult to control with the bar forward.

When you are always flying from a long runway you seldom need to worry about running out of space so its not something that you might think about.

Treat all heavyily loaded flights like a short field take-off.

Start as far back as you can at the threshold.
Build up power with brake on.
Build more spped on the ground before you try to rotate.

[WhiteEagle]

Here is a quick way of working out your density altitude: say for instance you are 4000 feet amsl. Tempreture outside is 25 degrees. Take 25 - 17 = 8. For every 4 degrees above 17 you add 1000 feet. In this instance your DA is 6000 feet amsl. Hope this help. There are a bit of humidity build into the calculation. There are more accurate ways to calculte the correct DA, but to difficult for me.

[John.com]

Here is a quick way of working out your density altitude: say for instance you are 4000 feet amsl. Tempreture outside is 25 degrees. Take 25 - 17 = 8. For every 4 degrees above 17 you add 1000 feet. In this instance your DA is 6000 feet amsl. Hope this help. There are a bit of humidity build into the calculation. There are more accurate ways to calculte the correct DA, but to difficult for me.

WhiteEagle, where does the 17 degrees come from?

Thanks,

John

[Duck Rogers]

Here is a quick way of working out your density altitude: say for instance you are 4000 feet amsl. Tempreture outside is 25 degrees. Take 25 - 17 = 8. For every 4 degrees above 17 you add 1000 feet. In this instance your DA is 6000 feet amsl. Hope this help. There are a bit of humidity build into the calculation. There are more accurate ways to calculte the correct DA, but to difficult for me.

Huh........?
And why bother getting an answer of 8 if you not using it?
Methinks I'm too old for this..

[Thatchman]

Duckie in his method its 8 divided by 4 degrees (2) times 1000 ft gives u the extra 2000 feet to get to 6000 feet.

[John.com]

This may be of use . . . . .

RULE OF THUMB – 50/70 http://www.mountainflying.com/Pages/mou ... _dist.html

The rule really is quite simple. It states: "Ten times the square root of the percentage of liftoff distance required is equal to the percentage of liftoff speed that should be attained in that distance." Egads, that sounds complicated; but it really is quite simple.

Airplanes stop better than they accelerate. It is possible to land at an airport where there is not sufficient runway available for the takeoff.

With this in mind we are going to mark the half-way point on the runway. If the airplane accelerates to this point and has the required performance, continue the takeoff. If the airplane arrives at the half-way point and does not have the required performance, abort the takeoff. The airplane can be stopped in the remaining distance, providing the airstrip is not downhill or has a wet surface.

We are going to use the half-way point of the runway for the "liftoff distance required." Keep in mind that this rule of thumb does not guarantee that the rate of climb will be sufficient to clear any obstacles that are present after takeoff, but it does guarantee that there is sufficient runway available for the takeoff.

Remember, this rule of thumb does not guarantee that the rate of climb will be sufficient to clear any obstacles after takeoff, but it does guarantee there is sufficient runway for the takeoff.

Mark the halfway point on the runway. This might require you to walk the length and count your steps, then walk back and determine a distinguishing characteristic or place a flag or marker at this halfway point.

Using the rule, "10 times the square root of the percentage of liftoff distance," we use 50 percent for the liftoff distance and the square root of 50 is 7.07. Ten times 7.07 equates to 70.7 percent of the liftoff speed. This speed should be obtained at the halfway point to guarantee takeoff in the remaining half of the runway. If you have the speed, continue. If you do not have the speed, abort the takeoff and wait for better conditions, or off-load some weight.

Safe Skies

John.com

[Blue Eagle]

ask a chick whose 90 Kgs to tell you shes 90 Kgs !!! wont happen bud, in her mind shes 80....

Hi Dish... a chick who is not a Pilot will not understand the importance of being honest about their weight. I had to disclose my weight to Demon in order to fly with him and knew the importance of being totally honest... naturally...

[Tailspin]

Here is a quick way of working out your density altitude: say for instance you are 4000 feet amsl. Tempreture outside is 25 degrees. Take 25 - 17 = 8. For every 4 degrees above 17 you add 1000 feet. In this instance your DA is 6000 feet amsl. Hope this help. There are a bit of humidity build into the calculation. There are more accurate ways to calculte the correct DA, but to difficult for me.

Or just use one of these.

[Biggles of Africa]

Good thread, thanks for sharing, so we can all learn from it.
John has pretty much summed up what I was going to say, a quick and easy way to determine the abort point is;
If you don't have 3/4 of your rotate speed half way down the runway, call it off.
Wind is your friend, as was mentioned, if you are in a situation where climb performance is marginal and you have a quartering cross wind, turn the aerie into wind as soon as possible so you can get the full effect of the wind to help you.
Now here is another little trick that sounds totally off base but works a charm.
If your climb performance is degraded for whatever reason, and there is an obstacle in your path that looks like you won't clear it with no way around it (within reason of course), don't try and out climb it, aim for it.
Let us assume you have just taken off and there is a row of trees at the end of the field, usually they are not a problem and you normally clear them by a hundred feet or more, but today Murphy is working overtime and for whatever reason, the aerie is not climbing as it should.
By trying to out climb the trees, all you are going to do is get onto the wrong side of the drag curve with the very real chance of a potential stall/spin accident.
By getting the nose forward and the airspeed up you increase the lift over the wing, by virtue of the increased airflow over the wing. So next time, don't point the nose above the trees, point it at the top of the trees, and as sure as God made little green apples, you will clear them just fine.
Of course this is within reason, not an excuse for flying overloaded, or trying to out climb obstacles that are obviously too tall to clear.

[Tumbleweed]

A simpler way is the 30% loss in performance. (difference to early morning take- off conditions)

30 Loss in power so requires that you either dump 30% weight - fuel used or loose the pax
Use 30 % more runway than normal (Take off point) i.e. 200 metres plus 30 % = 260m, call it 300 metres, before considering your 30% loss in climb to clear obstacles.

[bobthebuilder]

What a fantastic post!
Peter, I have learned plenty from your honesty. Thanks.