Buying a Seneca II

W

wjcoates

Filing Flight Plan
Joined
Feb 20, 2013
Messages
13
Display Name
Display name:
wjcoates
I am considering a Seneca II. I have about 1200 hours in a C206 and loved it for its ability to haul stuff. I will have my conversion training in the next couple of weeks but something has come up that I do not clearly understand.
What is Zero Fuel Weight (ZFW)? Is it the weight of the plane dry except for oil and other non-fuel fluids? If so, how is it related to the amount of load I want to put in my Seneca.
I know some of you must be shaking your heads wondering if I really have a pilot's licence, but in my 206 I knew with full fuel (80 gallons) I could put about 1000 pounds aboard and make it to the other end. I weigh 200, so 800 lbs. of stuff.
Basically I want to be able to fill my Seneca and fly but I am geeting different answers to how much I can load after full fuel.
In addition, one CFII told me the Seneca II is out of CG with full fuel and 2 persons in the front seat unless you load some 100 or more pounds in the back of the plane.
Can anyone assist?
 
Zero fuel weight is the total weight of the airplane minus the fuel. If the airplane has a maximum zero fuel weight that means that the weight minus all the fuel must not exceed that maximum zero fuel weight value. Basically additional weight above the zero fuel weight must be fuel.

If your gross weight is 4570 lbs and your maximum zero fuel weight is 4000 lbs. That means that anything above 4,000 lbs must be fuel. In other words if you subtract the total weight of the fuel the remaining weight must be 4,000 or less lbs.
 
Last edited:
Thanks very much.
The figures are as follows:
Gross 4570
ZFW 2841
Useful load 1729
The airplane holds 98 gallons that would weigh 588 pounds. So does that mean if I have 98 gallons aboard I can load 1141 pounds aboard-i.e. me at 200 pounds and 941 pounds of payload?
 
Having done ME training and some follow-up flying in a Seneca II, I can think of a number of other reasons to consider other alternatives. Just sayin'
 
wjcoates said:
Thanks very much.
The figures are as follows:
Gross 4570
ZFW 2841
Useful load 1729
The airplane holds 98 gallons that would weigh 588 pounds. So does that mean if I have 98 gallons aboard I can load 1141 pounds aboard-i.e. me at 200 pounds and 941 pounds of payload?
Click to expand...

That can't be right. ZFW should be like 4000 lbs. That means you cannot be 4100 lbs before adding fuel weight even if you are below gross with your fuel weight included.

The 2841 is your empty weight.
 
Last edited:
Thanks for that.
You are correct. The Standard empty weight according to Piper is 2841.
Unfortunately I am confused by the terminology and the Piper specs do not show a ZFW. However, elsewhere on the web I see a ZFW of 4000 lbs.
I am trying to determine how much I can load into the plane with full fuel at 98 gallons (588 lbs). In view of your comments can I assume I can load up to 4000-2841=1159 in the plane and have 4570-4000=570 pounds of fuel which works out to 95 gallons? If not can someone just ell me how much I can put in this plane and how it is calculated.
As it turns out the is 5 gallons of fuel unusable in the Standard Empty Weight so I have to figure in the other 30 pounds if I am correct?
 
wjcoates said:
Thanks for that.
You are correct. The Standard empty weight according to Piper is 2841.
Unfortunately I am confused by the terminology and the Piper specs do not show a ZFW. However, elsewhere on the web I see a ZFW of 4000 lbs.
I am trying to determine how much I can load into the plane with full fuel at 98 gallons (588 lbs). In view of your comments can I assume I can load up to 4000-2841=1159 in the plane and have 4570-4000=570 pounds of fuel which works out to 95 gallons? If not can someone just ell me how much I can put in this plane and how it is calculated.
As it turns out the is 5 gallons of fuel unusable in the Standard Empty Weight so I have to figure in the other 30 pounds if I am correct?
Click to expand...

Gross weight - (gallons usable * 6) - empty weight = Useful load
(The above is roughly correct. There are a few things that could change that like oil depending on how it was originally calculated. Would need to refer to POH and TCDS. But it's not going to make that much of a difference)

Zero Fuel Weight isn't going to apply if you're at full fuel already.
 
wjcoates said:
Thanks for that.
You are correct. The Standard empty weight according to Piper is 2841.
Unfortunately I am confused by the terminology and the Piper specs do not show a ZFW. However, elsewhere on the web I see a ZFW of 4000 lbs.
I am trying to determine how much I can load into the plane with full fuel at 98 gallons (588 lbs). In view of your comments can I assume I can load up to 4000-2841=1159 in the plane and have 4570-4000=570 pounds of fuel which works out to 95 gallons? If not can someone just ell me how much I can put in this plane and how it is calculated.
As it turns out the is 5 gallons of fuel unusable in the Standard Empty Weight so I have to figure in the other 30 pounds if I am correct?
Click to expand...

If you have the flight manual and it does not list a ZFW then I would think that none applies.

Re your question, what I would do is start with the desired fuel. If GW minus your desired fuel is less than ZFW then you can load to GW, other conditions like DA, runway length, etc., notwithstanding.

I think the ZFW situation comes in when you want to max out the cabin load and are adjusting the fuel to do that. In that case load the cabin to ZFW and see if bringing it to GW with fuel gives you enough fuel.
 
Thank y'all.
This all started because a CFII I was talking to about training threw in the "what is the ZFW" and I told him, and he told me with 1000 in the cab I could only load 35 gallons of fuel and that I should buy an Aztec to avoid that problem.
So, I am now happy with the info; I know I can load at least 1000 pounds aboard and still have lots of fuel. I fly to the Bahamas regularly and am buying this plane to haul stuff TCA deems is a threat to National Security like a spray can of insect repellant, cans of paint, car parts, light bulbs and other hazardous cargo that could Aerica as we know it.
I will keep you posted as I learn about wastegates and other fun stuff.
Thank you again.
 
wjcoates said:
Thank y'all.
This all started because a CFII I was talking to about training threw in the "what is the ZFW" and I told him, and he told me with 1000 in the cab I could only load 35 gallons of fuel and that I should buy an Aztec to avoid that problem.
So, I am now happy with the info; I know I can load at least 1000 pounds aboard and still have lots of fuel. I fly to the Bahamas regularly and am buying this plane to haul stuff TCA deems is a threat to National Security like a spray can of insect repellant, cans of paint, car parts, light bulbs and other hazardous cargo that could Aerica as we know it.
I will keep you posted as I learn about wastegates and other fun stuff.
Thank you again.
Click to expand...

YW. And, if you need some company on a flight, drop me a PM.
 
ZFW means a weight above which anything more needs to be fuel. For the Seneca II the SFW is 4000 lbs. So you have 570 pounds for fuel. I happen to have an EW of 3070, with a pretty full panel.....

So, you cannot put in a grand piano and 200 pounds of fuel.
Please note that doing "book" reasearch based on 2870 is totally BS. There is hardly a Seneca II on the planet, such that when you weigh her, is going to be under 2950 empty. You have radios. Autopilot. Transponder. Maybe a no radio Seneca II with only the front seats will be 2900. I have full Deice- a plate, boots and a regulator system. HD alternators.
This all started because a CFII I was talking to about training threw in the "what is the ZFW" and I told him, and he told me with 1000 in the cab I could only load 35 gallons of fuel and that I should buy an Aztec to avoid that problem.
Click to expand...
As for CG, that CFI-I has zero time in a Seneca II, and clearly doesn't understand ZFW. With the oxygen system in the back it down't matter what I put in the front seats. Seriously.

Now if you actually need 1000 in the cabin, you should consider a Navajo or a 414/421. When you first transition you need more than ever to fly 200 lbs undergross, until you can really do OEI. That last 200 lbs requires serious airmanship.

B
 
Last edited:
bbchien said:
As for CG, that CFI-I has zero time in a Seneca II, and clearly doesn't understand ZFW. With the oxygen system in the back it down't matter what I put in the front seats. Seriously.
Click to expand...

Yeah... He put ME in the front seat! :rofl:
 
wjcoates said:
I will keep you posted as I learn about wastegates and other fun stuff
Click to expand...
I would put a high premium on engines having had merlins on the exhaust elbow for the full life of the engine (since OH). It make the a/c a completely different bird, lowers EGTs, CHT, gives you a 19K critical altitude rather than 13K.

This is the ONE mod that is a MUST.

BACK TO THE PRIOR TOPIC, if you really intend to carry 1000 in the cabin, you need a larger bird, 600 hp is about right. Since you are new to multis, it can be established that you are not an ace.

I have what -3,000 in type, and I fly them 200 undergross, UNLESS I have 6500 feet of runway (as in, "Here's the keys to the CRV, boys. Meet me over at Byerly's" (10,000 feet)) where I can stop her on the runway. Once committed, I like to REALLY be able to depart on one, when a mill quits at 40" MP and 2575 rpm. The idea of taking the fence with 93 gallons aboard and five nonpilots with me....sucks enough that I never depart less than 6500 at gross....unless I am solo.

So, departing at 4575 is legal, but only SMART under certain conditions. And you won't find those conditions in the islands, except maybe at Nassau.

I'm not fond of thinking, "I'm going to burn to death".
 
Last edited:
The way to think of ZFW (that worked for me to understand it) is "what is the maximum payload in the cabin?"
The airframe can take X amount of pounds in the fuselage, the remaining weight is in the wings (fuel).

Weight in the fuselage applies force the wing roots, trying to fold the wings up. Weight in the wings does not try fold the wings up.
There are tip tank STCs for Bos and Comanches that increase the gross weight of the aircraft, but the extra weight must fuel in the tip tank, you can't use it in the cabin (for the same reason as above).

I don't know if the Seneca has wing lockers, and how that effects ZFW.
 
If you're looking for 1,000 lbs in the cabin, a Seneca won't do it. But an Aztec will, and gets similar speeds on similar fuel burn.

Cabin class is a big step. Only really makes sense if you need it for your mission. There's a reason we fly a 310 and not a 421.
 
Ted DuPuis said:
If you're looking for 1,000 lbs in the cabin, a Seneca won't do it. But an Aztec will, and gets similar speeds on similar fuel burn.
Click to expand...

I think the Seneca gets a few knots more on a couple gallons less, but certainly right in the same range, probably not enough to notice. Especially after the extra Mx $$$ with the turbos.

I was thinking about Senecas this morning, and the 1978 that I fly occasionally, I loaded up once. It only took three big guys to put it at gross, and that's after we drained fuel out to put it back at where it'd have been with standard tanks - This one has the long-range 123-gal tanks. I think we were at about 800 pounds in the cabin and 93 gallons of fuel to be right at MGW.
 
Ted DuPuis said:
If you're looking for 1,000 lbs in the cabin, a Seneca won't do it. But an Aztec will, and gets similar speeds on similar fuel burn.

Cabin class is a big step. Only really makes sense if you need it for your mission. There's a reason we fly a 310 and not a 421.
Click to expand...

What's the mission step that would make you go from your 310 to a 421? Just curious. =)
 
flyingcheesehead said:
I think the Seneca gets a few knots more on a couple gallons less, but certainly right in the same range, probably not enough to notice. Especially after the extra Mx $$$ with the turbos.

I was thinking about Senecas this morning, and the 1978 that I fly occasionally, I loaded up once. It only took three big guys to put it at gross, and that's after we drained fuel out to put it back at where it'd have been with standard tanks - This one has the long-range 123-gal tanks. I think we were at about 800 pounds in the cabin and 93 gallons of fuel to be right at MGW.
Click to expand...
Hey man, in fairness, you are a BIG guy. My whole family is 600 lbs.
 
flyingcheesehead said:
I think the Seneca gets a few knots more on a couple gallons less, but certainly right in the same range, probably not enough to notice. Especially after the extra Mx $$$ with the turbos.
Click to expand...

Part of it depends on altitude and also how you choose to run the engines. But basically it's in the same ball park. When Bruce had stated his numbers a few years ago it was almost identical to mine.

Apache123 said:
What's the mission step that would make you go from your 310 to a 421? Just curious. =)
Click to expand...

If somebody donated one. ;)

Or if we'd had quadruplets instead of one baby. The 310 makes an excellent family airplane for us.

wabower said:
I can think of a couple-hundred thousand reasons for openers.
Click to expand...

Those are the best reasons for not upgrading.
 
Apache123 said:
What's the mission step that would make you go from your 310 to a 421? Just curious. =)
Click to expand...

Long trips with pax that do not want to wear 02 would be the biggest I guess. 421 is turbo so it can do FL for a bit better speeds over a 310. A 320 might keep up but have to wear 02.

Prestige might be another as in flying around CEO of medium corp.

I think in the B model 421 you can add a 7 person.
 
bbchien said:
Hey man, in fairness, you are a BIG guy. My whole family is 600 lbs.
Click to expand...

Yep - The point merely that in that particular bird, 800 lbs and 93 gallons (full for the non-long-range-tanked Seneca II's) had us right at gross, so 1000 lbs and full fuel probably isn't gonna work. 800 and full fuel, or 1000 and 60-ish gallons...

Not knockin' the bird at all! I like 'em. :)
 
flyingcheesehead said:
Yep - The point merely that in that particular bird, 800 lbs and 93 gallons (full for the non-long-range-tanked Seneca II's) had us right at gross, so 1000 lbs and full fuel probably isn't gonna work. 800 and full fuel, or 1000 and 60-ish gallons...

Not knockin' the bird at all! I like 'em. :)
Click to expand...
1000, and 93 gallons, or 800 and 123 gallons puts you at gross.

But I'm more cautious than that. 800 and 93 gal is the order of the day.
 
bbchien said:
1000, and 93 gallons, or 800 and 123 gallons puts you at gross.

But I'm more cautious than that. 800 and 93 gal is the order of the day.
Click to expand...
Bruce's family and a Seneca II == perfect match. :D
 
You must log in or register to reply here.
Back
Top