Takeoff incident

Good points in relation to a potential tailwind; it is always hard to know (after the fact) exactly what might have occurred. Although the OP said they were not ‘nose high’, I have definitely had something similar happen, twice! Both times, I was flying a 160hp PA28 at gross weight off a grass runway.

Typical Canadian PPL training covers both short field, and soft field take offs, so after getting my license I was eager to apply both techniques as per my training. I know they have been discussed above, but I will recap for clarity.

The requirements for a short field take off are obvious, i.e. minimum drag until lifting the nose at the correct take off speed. However, this may not quite jibe with the POH which suggests having the flaps down to the POH setting for the whole take off run.

The idea with the soft field take off is to have the flaps down, and the nose held high for the take off run. The exact ‘nose high’ configuration will depend on the hp available and the mass of the aircraft. The idea is to have the main wheels lift off the surface as soon as possible, which results in the AC ‘staggering’ into the air with a high angle of attack (this is definitely on the back side of the power curve, and depending on how aggressive the maneuver, could be on the verge of a stall). As long as there is excess hp available, you can continue to accelerate in ground effect easing the nose down to a normal angle of attack as the aircraft picks up speed. Problems occur if there is too much drag from the angle of attack, and no excess power available….

Now onto my situation. The first time this happened, I was at a very long grass runway, which was a bit wet. I elected to choose a soft field take off, but not with a particularly aggressive nose-up angle as I didn’t want to alarm the passengers (one of them being my mother!). About a quarter of the way down the runway, I noticed we were no longer accelerating at the normal rate. I didn’t perceive anything wrong with the power, but instinctively lowered the nose. After doing so, we picked up speed and were airborne. I filed a mental note away… thinking, hmm there must be a lot of combined drag, from the grass, soft ground, the flaps, plus the induced drag from the angle of attack… better watch out for that one!

The next time this occurred I was at a shorter grass runway (but still plenty of room say ~800m) on a warm summer day, again at gross. It was dry but bumpy, so I opted a soft field take off with the flaps down and nose up (again not ‘aggressively’ up). About half way down the runway, it was obvious that this take-off configuration, plus the drag of the grass, was not going to work and I was at risk of being in the trees at the end of the runway. I aborted, stopped before the end of the runway and circled back. Static power checked ok, so I opted for a minimum drag take off configuration, i.e. no flaps, elevator neutral and nose on the ground. At, or just prior to, flying speed, I popped in two notches of flaps, lifted off the ground and flew away. On the second attempt, I was probably climbing well as I passed through the point which I had aborted on the previous attempt.

After this ‘lesson’ I am now quite cognizant of the drag induced from the nose high angle and the flaps. When it really matters for short strips (even if muddy or bumpy) I now always accelerate in minimum drag and put the flaps down at the moment flying speed has been reached. Probably best to experience these things with some circumspection and practice before you ‘need’ to use them.

I would also point out that practicing take offs in the PA28 on grass with half fuel and only the pilot, is much different than at gross weight. In both of my incidents (at gross) , I did not initially think that the nose was overly high. Certainly in solo practice I was able to take off with higher angles of attack.

Although not specifically related to the OP, another similar situation has jumped into my memory. This was a one way down hill strip which was a mud bog. I had already been stuck once… after getting the AC out of the mud bog (strangely I think my Mother was on board for this one too!) I lined up for take off. All checks ok, but acceleration was a bit slow. This is hard to evaluate, because you are thinking downhill=faster, but mud=slower. Anyways, as per above, I probably lowered the nose a bit… we accelerated but were closer to the end of the runway than I would have preferred. After an uncomfortable moment, it was up and away as per normal. On the next landing, which was home base on a paved runway. I was shocked to land and do the shortest roll out ever. Apparently, in all the fuss of being stuck, I had left the parking brake on ‘one’ notch (which is not entirely obvious in a Cherokee), so although the wheels were not locked, there was substantial braking! This, of course, explained the slower than normal take off. I can only imagine the ruts we left behind.

And they say a pilot’s license is a license to learn… :-) Or is it that you ‘had better fill you bucket with experience, before your luck runs out…’

Magnus, Canuck,

the trick to lower the flaps during the take-off run is absolutely not recommended. The risk to lose control of the airplane while reaching down for the flap handle absolutely outweighs the little gain you might have from doing that stunt. You also have to take the hand off the throttle, and that’s something I never do when taking off from a short field.

Better: Do a short field takeoff with 25 flaps, accelerate in ground effect and climb with Vx if there are obstacles or Vy if there’s no obstacle.

I think everyone agrees that the POH says either 0 or 25 degrees for take-off. The thing is that in Sweden a lot of PPL students are taught to use Flaps 10 for take off on normal take-off (at least in PA28). Been there, done it as I did my PPL in Sweden. I think it’s a bit like so called ‘Old Wifes Tales’ – everyone is being taught it’s just ‘better’ without necessarily the right facts to back it up. I believe the main reason for this wide spread practice is that it is believed to give extra safety margin to stall on the climb out if the student is sloppy on managing IAS and/or wind is really gusty and/or one is seriously heavy and barely gets to right IAS at rotation before runway ends. As someone was being taught, it’s believed to give better ‘stability’.

I’ve also seen the practice on short / soft field to leave flaps zero and only set it when really needed but I’ve never liked the practice to get distracted and start operating the flap at the exact right moment to optimise the whole take-off run… seems less than ideal when one carefully needs to monitor speed, runway available, maintaining centreline etc to start moving one hand from control wheel or throttle at these critical moments. In addition I cannot believe the difference in take-off roll will be really different if accelerating with zero flaps vs e.g. 25 degrees flap in the case of a PA28…

See that Flyer59 made the same comment as me re lowering flap on take-off roll now that I had posted…

Apparently, there are critical down-sides with that method.

Somewhat related to short field take off: What about standing on the brakes with full throttle to decrease take off distance?

That’s an interesting one! I once wrote an article for a flying magazine about that method – and while our research was in no way scientific it seemed to us that it really makes no difference: Stand on the brakes and wait until you reach the highes rpm or just make a normal takeoff … the difference was marginal, at the best. What worked better was a rolling takeoff… advancing power wile taking the runway.

You know why some schools teach the 10 flaps method in Pipers? Some CFIs think it’s a good method to train pilots for heavier planes, and this way you can do a full “after takeoff checklist”. That’s no problem if you take of from a normal airport – but it has no aerodynamic advantage, i think.

For the same reason some schools install a GEAR SWITCH with three green lights in Cirrus planes :-) YOu can buy that as an accessory.

I did my original training and license in the US and short / soft field techniques were most definitely taught. However, that certainly didn’t include ‘staggering nose-high into the air’! It was always: get off the ground (flaps as per POH) and then nose down and accelerate in ground effect until flying speed is reached, then climb and retract flaps one stage at a time. I’ve never done the ‘flaps during t/o roll’ thing and in any case, in Cessnas (which is what I mostly fly) this probably wouldn’t work well, as they are operated electrically and come out relatively slowly. In a PA28 of course you can yank them out with the ‘handbrake’ lever.

As to the ‘stand on the brakes and rev the engine to max’ before a short-field t/o, this was indeed the standard technique. I never did comparative tests, but also doubt it makes much difference. However, +1 for the rolling takeoff, this does make a difference.

I know this is controversial because it is a bit “airliner-ish”, but a bit of flying by the numbers helps.

Many POHs have speeds on when to start to lift the nosewheel, and when you start to pull back into climb attitude at that speed, you pretty much end up at Vx / Vy very shortly after lift off. Any earlier and it gets mushy, any later and you don’t get the book performance. The temptation is to lift off too early, and that definitely does not help.

This applies to short field on a hard surface or firm, short grass – on a draggy surface, you WANT to lift off early – as172driver says.

When I started to take a Turbo Saratoga into shorter fields (like Muckeburgh or Aachen) I played around a lot with technique, and – surprise, surprise – the POH was spot on. Take-off pretty much 1:1, landing roll a bit conservative.

Interestingly enough, in an aircraft with a medieval turbo system, setting full power (or a couple of inches less, because of the medievalness) when lined up DOES help, because you can get full power earlier in the take-off run and don’t have your head in the cockpit to fiddle with the throttles.