Getting to know the Seneca

Kent,
I living vicariously through your Seneca experiences. Great questions, along with some great answers. Does the POH give the formulas to calculate the take-off roll and the accelerate-stop distances ? What's the shortest runway you would consider operating out of in the Seneca ?

NC Mountain
NC Beach
 
jdwatson said:
Kent,
I living vicariously through your Seneca experiences. Great questions, along with some great answers. Does the POH give the formulas to calculate the take-off roll and the accelerate-stop distances ? What's the shortest runway you would consider operating out of in the Seneca ?
Click to expand...

There aren't formulas, but there are performance charts. As noted, we were basically at gross and the accelerate-stop was 1900 feet, though the cold weather certainly helped.

I think I'd probably want 4,000 feet at this point, as I haven't yet had the opportunity to test the limits with the plane or get to know it much. In the mountains, surrounding terrain and single-engine performance would probably be a more limiting factor than runway length.

As far as what the plane is actually capable of, Dr. Bruce is an expert on real-world Seneca performance. :yes:
 
flyingcheesehead said:
There aren't formulas, but there are performance charts. As noted, we were basically at gross and the accelerate-stop was 1900 feet, though the cold weather certainly helped.

I think I'd probably want 4,000 feet at this point, as I haven't yet had the opportunity to test the limits with the plane or get to know it much. In the mountains, surrounding terrain and single-engine performance would probably be a more limiting factor than runway length.

As far as what the plane is actually capable of, Dr. Bruce is an expert on real-world Seneca performance. :yes:
Click to expand...

Kent, I could be wrong (I don't have any Seneca manuals) but I really doubt that any Seneca filled to max gross weight has an accelerate-stop distance of 1900 ft at any altitude. Double that seems more like it. Any chance you are only including half the picture (accelerate or stop but not both)?
 
lancefisher said:
Kent, I could be wrong (I don't have any Seneca manuals) but I really doubt that any Seneca filled to max gross weight has an accelerate-stop distance of 1900 ft at any altitude. Double that seems more like it. Any chance you are only including half the picture (accelerate or stop but not both)?
Click to expand...

Lance,

T/O roll was calculated as 1100 and this particular bird has the optional heavy-duty braking system installed. For the conditions that day (nice and cold), 1900 was indeed the full accelerate-stop distance according to the POH.

Realistically, we weren't doing short-field technique (7200 feet of available runway) and the odd power addition on the Seneca means you're not really up to full power for at least a couple hundred feet (I'm not anyway, I'm sure Bruce knows how to do it a lot quicker than me) so it does take longer in real life. Amazingly enough, both climb rate and cruise speed met book values exactly. Not bad for a 12,000-hour airplane.
 
flyingcheesehead said:
Lance,

T/O roll was calculated as 1100 and this particular bird has the optional heavy-duty braking system installed. For the conditions that day (nice and cold), 1900 was indeed the full accelerate-stop distance according to the POH.

Realistically, we weren't doing short-field technique (7200 feet of available runway) and the odd power addition on the Seneca means you're not really up to full power for at least a couple hundred feet (I'm not anyway, I'm sure Bruce knows how to do it a lot quicker than me) so it does take longer in real life. Amazingly enough, both climb rate and cruise speed met book values exactly. Not bad for a 12,000-hour airplane.
Click to expand...

Ah! but how about the accelerate-go distance? Big brakes won't help there. I'd bet that's longer and you don't have a balanced field without both. Plus the reality is that until you have the gear up and are climbing at Vyse with 100+ feet between you and the ground or above Vyse by 15-20 Kt, you aren't really able to continue on one. Figure another 1000 ft past the book numbers just for that.
 
wouldn't just add the T/O roll to the Accelerate-stop distance ?
 
jdwatson said:
wouldn't just add the T/O roll to the Accelerate-stop distance ?
Click to expand...

Accel-Stop is the sum of the distance needed to get up to rotation speed (typically VMC+5) and the distance needed to stop from that speed. Accel-Go adds the first part of Accel-Stop to the distance needed to clear a fairly low obstacle assuming the critical engine (the one that causes the most yaw when it quits) dies exactly at the point where you reach rotation speed. The promise is that if you have rotated at the specified airspeed you should be able to climb far enough above the runway (in ground effect) to raise the gear and then edge your way up to Vyse (best rate on one engine) after feathering the windmilling prop, reaching a towering altitude of 35 feet by the time you get to the Accel-Go distance from the start of your takeoff roll. The reality for most light twins at MGW is that you might be able to pull that off if the engine doesn't quit until you are close to 100 AGL and above Vyse. Even that's assuming you react correctly and expeditiously to the engine failure.
 
You must log in or register to reply here.
Back
Top