PA 34-200 perfomance question

[will fly for food 06]

Hello.
I was wondering if someone could kindly help me please. I am flying a seneca 2 at the moment and have question regards performance calculations. The books i have are only able to calculate the take off distance with no flap. However when taking off from short grass strips 2 stages of flap is required. Does anyone have a POH with the graph for take off with flaps or a factor i could use?

Thanks in advance.

[hugh flung_dung]

Not a full answer, but ...

If you look around you should be able to find a copy of the Piper PA34 book which looks like a flight manual but is actually more sales info (sorry, can't recall what it's called and I don't have a copy here). This book has systems info and perf data with and without flap - but the data is VERY optimistic and would probably be unsafe if used by itself.
An unofficial but defensible technique is to take the case you're interested in (WAT, etc) in the "sales" book to get the distances with/without flap, then use these to calculate a "flap factor" which can be applied to the calculated distances from the official manual.
Obviously this is an unofficial technique but it gives you something to work from. ISTR that for a Seneca 1 at MTOW the TORR factor is about 0.78 and the TODR factor is about 0.86 - these reflect reality quite closely for typical UK conditions.

HFD
(Remember that this is worth what you paid for it ;-) )

(small edit to fix typo)

[vanHorck]

I own and fly a Seneca IV.

Most of my flying is done out of Fowlmere (EGMA), the best Piper base in the UK, but also a grass strip of just some 700 metres..... That is plenty, even on wet grass.

I NEVER use flaps in a Seneca for take off. If you had an engine failure on take off, you d never recover in time. NEVER.... NEVER!

So simply never fly your PA34 out of a strip that is so critical you need flaps for a take off.

I would not fly out of a strip below 600 metres on a normal day. That means I dont land there.

Its just my opinion......

[will fly for food 06]

Thank you for your replies. You have brought up some interesting points. I am used to flying off small grass strips in singles(450m) but not on the seneca as yet. Still trying to get a feel for her after flying the duchess before. The seneca operates from a grass airfield of just over 700m but i dont think id like to have a go landing there on short wet grass in light wind.

[englishal]

I NEVER use flaps in a Seneca for take off. If you had an engine failure on take off, you d never recover in time. NEVER.... NEVER!
The PA34-200T short field technique is indeed 2 stages of flap. Goes up like a helicopter too. I see what you are saying but sometimes it is better to get up high faster....

[will fly for food 06]

Interesting regards the no flap take off. Brings up alot of thought regards engine failures soon after take off. Standard brief from CFI during check out was the take off with two stages of flap and rotate at 77 Kias. The aircraft seems to want to get off the ground well before the quoted Vr. We have a V2 of 89 and a Vmca of 69. I certainly wouldnt want an engine failure at Mtow or close to it soon after gear up. That situation is one of the main things I run through in my head before lining up. Has anyone here had an engine failure at Mauw in a seneca and managed to climb?

[vanHorck]

I like this exchange of views, content!

The great benefit of a Seneca is the speed an stability in the air, leading to comfortable longer trips. Flown the Seneca (return) from Fowlmere to Bucharest (one stop in Linz) and from Bucharest to Jerez (stops in Pescara and Palma) as my two longest trips.

But given the poor climb and cotrolability at low speeds I just would not land in a PA34 on strips where i know i will need flaps for take off.

700 metres on wet grass is light winds is doable providing you know the approach well and with the slow and low approach. Even better if two pilots, and P2 retracts the 3 stages of flaps immediately after touch down. Not only this increases the grip on the grass (allowing for more breaking action without skidding) but it prepares you a go around should you need it.

I found the issue with the Seneca was a heavy nose, so i trim back in the flare, and this makes for great landings , but you need to be ready to trim forward on a go around immediately (electric).

There is no light twin to beat a Seneca. No Eurocharges, good speed, available spares, proven icing conditions, reasonable single engine climb.

In my view (I m old fashionned) the best ones are late models with traditional instruments including radar and a simple moving map. Hence my immaculate G-MAIK PA34-IV. She even has oil based paint still (as opposed to the current water based) and this means that after 13 years the paint still looks great!

Enjoy!

[Tony Hirst]

Interesting regards the no flap take off. Brings up alot of thought regards engine failures soon after take off. Standard brief from CFI during check out was the take off with two stages of flap and rotate at 77 Kias.No wonder, the rotate speed for a Seneca 1 with 25 flap is 65 kts. What is interesting about the performance t/o is that the POH states that one should climb at Vx until x00' whereas due to lack of obstacles beyond the threshold at the place I flew it from, the technique is to hold the nose down and accelerate. The problem with the latter is it takes a significant amount of time to get to Vsse, chewing up all the available runway in the process with absolutely no room for manoeuvre. I'm open to thoughts on that.

A short field landing requires a firm touchdown with the stick held hard back and the flaps retracted to aid braking. It can stop in fairly short order. No flown onto wet grass yet, but I think the factors are in the POH, if not then the CAA/JAA ones should be applied.

[vanHorck]

it is correct to fly the plane in ground effect till (well above) blue line speed,
As the acceleration is much faster without flaps, that too is an argument to take off flapless.

Of course this depends on available runway and obstacles at the treshold.

Fowlmere (EGMA) has the benefit of no obstacles at the end of of 25 but anyway you can achieve blue line speed there even on wind still days well before the end of the runway

Main items are a clear briefing on abort/continue, use ALL the runway and power up on the brakes for as long as you can before releasing the brakes

Contact Derick Gunning at Fowlmere (Modern Air) and see if he s willing to instruct you a bit on grass short fields take off s and landings in a Seneca . The man is a exceptionally good instructor and the aerodrome seems to be what you need to get your confidence and understand your own limitations as well as the plane's.

Good luck!

Bert

[will fly for food 06]

Thank you for the information. I will have a look at the new lower rotate speed. What are you using as Vat?

[SNS3Guppy]

I flew Seneca II's and III's doing ambulance work from rough dirt fields in remote locations, and often used flaps for takeoff.

For takeoff distances, use the no-flap distances. Any takeoffs with flap will be shorter, making your takeoff calculations conservative.

Due to the field conditions, to preclude flap damage, flaps were usually left up until the takeoff roll was well established, then applied.

[eyeinthesky]

I seem to remember someone recommending accelerating with no flap and then applying two stages just before Vr. This had several advantages: no flap damage as already identified; reduced drag in the initial acceleration; it made the ground break almost instantaneous and the lift above hedge height pretty quick. It then required some judicious calculation of lift vs drag to get them retracted with minimum sink.

It would of course be helpful if you had another hand to do that for you so you can keep your own hands on the yoke and the levers to keep them forward...

Of course, if the flaps should deploy asymetrically, you're on your back doing 60kts before you can blink!

Never tried it myself, but I wonder whether such techniques, if they are required to get out of a certain strip, mean that the risk level of using the strip in the first place is not too high!

[hugh flung_dung]

I've been teaching in a Seneca 1 from 781m of grass for many years; it's totally straightforward with correct techniques. The short field grass takeoff technique is to use flap 2, set the yoke 2/3 of the way back and let the aircraft leave the ground when it's ready, then accelerate to reach Vyse by your pre-briefed "go" height. The approach technique is standard (maintain Vyse and flap 2 to Vach, then full flap and slow to Vat). The Seneca 1 Vat is 75kts (+5 if asymm or flapless).
If you're not comfortable with this then a check with a suitable FI would be good.
I'm hopefully teaching you to suck eggs here but always pre-brief the departure with something along the lines of: problem on the runway=power off and max braking; problem airborne below Vtoss and 200ft= power back, lower nose, use available power to reach best landing area; problem above Vtoss and 200ft= control, gear up, flap up, identify, etc, etc.

HFD

[Lost man standing]

vanHorckI NEVER use flaps in a Seneca for take off. If you had an engine failure on take off, you d never recover in time.That's always a possibility in something of that marginal performance. It is also a certainty in a single, but it shouldn't stop anyone flying! Just remember that on any departure in a piston twin a forced landing should be briefed as alternative to a circuit in event of EFATO.

Certainly any of the PA-28/32/34 series should get similar performance benefit from a couple of stages of flap. There isn't such a great difference between them, is there?

The data should all be in the flight manual for the aircraft.

[SNS3Guppy]

If you had an engine failure on take off, you d never recover in time.


That's just not true.

[vanHorck]

perhaps i should rephrase

the deceleration with flaps in case of engine failure is higher than without flaps (more drag).
The time to establish which engine failed and taking the appropriate action and stabilize the plane is always going to be a few seconds. These seconds can be critical.

Especially the time between rotation (at rotation speed) and reaching (more than) blue line speed is the dangerous part

I would still elect to only land at strips which do not require me to use flaps for take off. But it s just my decision, everybody is free to have their own opinions