I contributed to this thread in 2014. I can add a few more now:
Don’t do a checkride not knowing the GPS.
Don’t pick the wrong mechanic.
Don’t overhaul engines and expect it to increase market value.
Don’t start another business venture, rebuild your house, start a family and restore an old aircraft at the same time.
Had six sectors to hit up collecting my cirrus, so automatically behind the time curve. Flying a husky always with the perceived satisfaction that I can land pretty much anywhere, took off into alleged improving met… Cloud base getting lower and lower but still 1000 ft over the fens. Not IR at this point. nice little six pack in the husky and SkyDemon. 800 ft. 700 ft. Then a layer below me appearing. Turn around. Ah. Layer building below here too. 50 50 ground vis. So now down to 100. Field land. Stop shaking after around 20 minutes. Muppet.
Ok. Confession time. This was likely my most stupid mistake in 21 years of flying.
A few days ago I made a flight with a PA-28-181 at max weight, taking off from an airfield with a 680 m grass runway. The temperature was 26°C.
My home airfield has 630 m grass and my experience is that you never have problems getting airborne even in zero wind. I even made a calculation once that showed that up to 30°C that runway has sufficient length.
There was a direct crosswind, so no headwind component, but anyway this should be a piece of cake. Oh, the airfield elevation was 1000 ft higher than my home airfield, but that small difference in altitude shouldn’t matter, right? WRONG. I did get airborne before the end of the runway but if there had been obstacles in the climb-out path I would have been in serious trouble.
After coming home I calculated the take-off distance required (to 50 ft) and it was 755 metres.
And what about the runway at my home base being sufficient up to 30°C? That was for a Cessna 172S…
Lessons learned:
Familiarity breeds contempt.
Never take anything for granted.
@Airborne_Again the Warrior chart shows 670m at that DA, before adding a grass safety factor of 20%, albeit over a 50 foot barrier. Am guessing the Archer is 50-100m shorter over 50 feet?
Thanks for posting, I think I will use the 70% of lift off speed by 50% of TODA into my take off brief. Optimal technique in the Cherokee on a short grass runway is tricky. You need stick back initially to avoid drag from the nose gear, but then relaxing to level at the right time to avoid aerodynamic drag, and ideally going from one to two notches on the manual flaps to add some pop to the lift off. Cessnas do seem to fly off grass while keeping the stick back, but then the majority have electric flaps.
Years of Super Cub means sometimes a grass field looks much longer than it is!
Airborne_Again wrote:
Familiarity breeds contempt. Never take anything for granted.
On same day with a light C172 and very tall grass, takeoff at 11am was about 300m, takeoff at 1pm was about 800m, between the two takeoffs we had some heavy showers (I did make right call to wait for the sky is clear but that only shifted problem: the rain was sitting on the ground and wind dropped to zero )
Runway length was a generous 1200m but I am still puzzled how come I did not reject at 300m with wheels+ASI stuck for ages on 40kts?
Thanks a lot for sharing this.
A few years ago, we had an accident with a PA28-180 out of a similar runway, where again, ground roll was fine, but 50 ft was well after the runway end. That guy panicked and stalled the airplane, crashing it. Luckily nobody got hurt, the airplane was toast, but the lessons were very valuable as DA is something which also is very relevant at perceived low altitude.
What this is known is a take off from an unbalanced field lenght. Usually this is for airliners, but it also works for us.
Airborne_Again wrote:
After coming home I calculated the take-off distance required (to 50 ft) and it was 755 metres.
Looking at my copy of the Archer Manual, here some figures. If I get it correctly that 680m runway was at approximately 1100 ft AMSL, Temperature 26°.
Piper does not provide for grass effects and I assume for the moment, that with the heat wave you guys had, your grass runway was very dry :)
With zero flaps, I am getting a ground roll of apprx 450 m and a total distance, as you said, of 760 m.
With flaps 25, the ground roll would be about 400m and the total distance 640m.
Using the factored lenght for grass with the general factor of 1.33 you get:
With zero flaps a roll of 600m and total distance of 1023m
with flaps 25 a roll of 532m and a total distance of 851m.
So the good news is that even with the most restrictive calcs the runway was absolutely long enough to get airborne.
As you said, the important bit is the total distance. While it is not necessarily required to reach 50 ft within the runway lenght, it is important to know that you won’t and therefore a determination can be made if obstacle clearance allows for an unbalanced take off where the 50 ft “obstacle” is overflown after the end of the runway.
TORA (Take Off Run Available) was 680 m. The question would be, what the TODA (Take off Distance Available) is, which includes any sort of clearway after the runway, in practice how much empty space at the same level as the runway is available beyond the runway end.
In your case, this obviously worked and it can work quite well. What got my attention in the accident report I mentioned above is the startle effect once a pilot realizes that he will rotate much closer to the runway end than usual and overfly the runway end at less than 50 ft.
with the very short runways available at some places, some of which I am intimately familiar with, unbalanced take offs if planned accordingly work just fine. In fact, e.g. at Wangen Lachen, a 500m runway at the lake of Zurich, the majority of take offs will be unbalanced, let alone in places like Helgoland and similar.
It’s also quite important to look at the effect of flaps for this kind of take off. Flaps 25 will significantly reduce both roll and total distance.
Take off (and landing) calcs are always something one can play with quite extensively and in the day and age of Excel it is relatively easy to make yourself tables for the information the POH does not provide, e.g. factored lenghts for grass.
I’ve experienced take offs like the one you did several times and they can be quite scary, but at the same time, planned properly, can enhance the utility of the airplane significantly. Believe me, my reaction was the same as yours…
Thanks again for sharing. Great example and highly relevant for Summer.
Mooney_Driver wrote:
Looking at my copy of the Archer Manual, here some figures. If I get it correctly that 680m runway was at approximately 1100 ft AMSL, Temperature 26°.Piper does not provide for grass effects and I assume for the moment, that with the heat wave you guys had, your grass runway was very dry :)
With zero flaps, I am getting a ground roll of apprx 450 m and a total distance, as you said, of 760 m.
With flaps 25, the ground roll would be about 400m and the total distance 640m.Using the factored lenght for grass with the general factor of 1.33 you get:
With zero flaps a roll of 600m and total distance of 1023m
with flaps 25 a roll of 532m and a total distance of 851m.
The grass was indeed very dry, short and well kept.
The QNH was a couple of hPa above standard so the pressure altitude was almost exactly 1000 ft. At a temperature of 80°F (26.7°C) the POH for my aircraft gives a roll distance of 360 m and a takeoff distance of 686 m for a hard runway with 25° of flaps. The POH doesn’t give any corrections for grass runways, so I’ve used +10% of the total distance which was the figure in the Swedish national regulations before part-NCO. That gives 755 metres.
What was even more stupid of me was that I used Autorouter for flight planning and had I bothered to check, I would have seen it had calculated almost exactly the same figure!
As you say, given that the roll distance was well within the runway length and the terrain was reasonably flat, there was no actual danger. I didn’t even get a comment from my ex-PPL wife in the right seat who otherwise is quick to point out when she thinks I’m doing something questionable.
Airborne_Again wrote:
The POH doesn’t give any corrections for grass runways, so I’ve used +10% of the total distance which was the figure in the Swedish national regulations before part-NCO.
That is a very common problem with older airplanes. The fun bit in the Archer manual, which I checked last night, is that it sais you have to take into account corrections for grass but doesn’t give any. There are many recommendations for generic facturing of runway lenght. I took the factor of 1.33 which I was told once, but which in your case was most probably over conservative as it takes into account wet grass. Dry grass and 10% sounds very reasonable. Sometimes, it may be challenging to figure out the actual calcs for such airplanes where the POH is lacking. And it may well take such experiences to look into it with more depth, which definitely is a very good thing.
Unbalanced field length is not something dangerous or even scary if it’s planned. In my time as a dispatcher, for the long haul flights it was the rule rather than the exception. It can look spectacular but if the calcs are done right it works quite reliably. At least, in the day and age of google maps it is relatively easy to figure out if there is a clearway or not.
And sometimes, after it worked, one finds out that the calcs agree. Been there and might design a t-shirt if I get the chance 
Again thanks for posting.
(although that Bournemouth takeoff isn’t nearly as close as it looks – the very long telephoto lens makes it look a lot more dramatic than it really was!)
alioth wrote:
(although that Bournemouth takeoff isn’t nearly as close as it looks – the very long telephoto lens makes it look a lot more dramatic than it really was!)
I know but I could not find the IL76 in Australia on the quick. But as I aim to please, here it is. It doesn’t come more unbalanced than that without an accident…
But believe me, I’ve seen some take offs at ZRH by Tower Air, Pan Am and PIA which were VERY much closer. Several lifted off beyond the TORA, without too much effect as it is still runway but some of those take offs were pretty low overhead Glattbrugg. All of these were unbalanced take offs.
And then we had the case of a Pan Am 747-100 which lost an engine on rotation and started dumping with the main gear still in touch of the runway…. he made it out but that was the scariest thing I’ve ever seen. I was not there for the Continental 747 at LGW who almost took Russ Hill with him but that was probably the worst one.
(the A340-100/200 s another one of those…. but there the reason mostly is that it is flown on reduced take off power rather than not having the thrust available)
