Ventus bT/cT comparison

On Tue, 17 Apr 2012 12:46:24 +0000, Jim Pengelly
wrote:

Hi everyone,

I fly a Discus bT at the moment and absolutely love it. However, I
am thinking of upgrading to a flapped turbo in the next one or two
seasons and the Ventus bT/cT would seem to be the natural
choice.

I have heard conflicting opinions about the various models:

i) The bT has handling issues and the cT was designed to
overcome these issues, with a bigger rudder and some other
changes. The cT is the model to go for.

ii) The cT has handling issues, can be difficult to bleed approach
energy due to the brake configuration and was not a popular
model, which is why there are so few of them around. The bT is
the model to go for.

iii) The bT and cT perform relatively poorly in 15m mode rather
than their 16.6m (bT) and 17.6m (cT) modes, so competing in
15m mode is not recommended.

Any thoughts much appreciated.

Cheers,
Jim


I'll offer a few comments. My Ventus cT is a 1987 model and I've got
about 1500 hrs on the ship over the past 13 years.

-- One possible reason for the apparently small number of C models in
the US is that at least the early C's were brought into the US as B
models, and then re-placarded as a C model. My '87 cT has the original
B placard still in place, but X'd out with the new C placard mounted
below it. I notice that a number of Ventus B models in the FAA
database are in fact C models whose owners never updated the FAA
records.

-- I've got no complaints regarding the handling of the Ventus C,
thought I fly almost exclusively with the 17.6m tips. I've noticed no
issues with handling with the 15m winglets, however.

-- Unfortunately I have never had to opportunity to fly a Ventus B.
The only unbiased comment I can quote is from Derek Piggott in the Dec
1992 / Jan 1993 Sailplane & Gliding issue.

"Whereas the earlier model has rather a reputation for stalling and
spinning if flown carelessly. the C model seemed a model of docility.
I frequently pulled into steep thermalling turns, getting down to well
below 40kt with only an obvious buffeting and sinking feeling clearly
indicating that this was far too slow. It did not once drop a wing
requiring any proper stall recovery. In spite of the extra wing span,
the rate of roll is excellent at all speeds and it is easy to fly
accurately rolling into and out of turns"

-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first. For my weight and 28
gal of water, I hit max gross just before I hit the non-lifting limit.
Bottom line, with the engine in place and ballasted to max gross, you
are at the same loading as without the engine, but you cannot dump
down to the same low loading as without the engine. With the engine
in, I can go from 10.1 lbs/ft2 max down to 7.9 lbs/ft2 min. Without
the engine, W/L ranges from the same 10.1 lbs/ft2 down to 7.2 lbs/ft2
(all with 17.6m span). The B model has the same issue and limitations.

-- For what its worth, only the C models were factory certified with
the 17.6m tips.

-- Regarding the air brakes, I have never found a situation where
landing flap and full dive brakes were inadaqute. That said, they
probably are not the equal of a PIK 20B or any other ship with full
90deg flaps (I've got about 2500 hrs in a 20B, before the Ventus).

Hope this helps your decision.

Bob

At 03:36 18 April 2012, Bob Gibbons wrote:
On Tue, 17 Apr 2012 12:46:24 +0000, Jim Pengelly
wrote:

Hi everyone,

I fly a Discus bT at the moment and absolutely love it.
However, I
am thinking of upgrading to a flapped turbo in the next one or
two
seasons and the Ventus bT/cT would seem to be the natural
choice.

I have heard conflicting opinions about the various models:

i) The bT has handling issues and the cT was designed to
overcome these issues, with a bigger rudder and some other
changes. The cT is the model to go for.

ii) The cT has handling issues, can be difficult to bleed
approach
energy due to the brake configuration and was not a popular
model, which is why there are so few of them around. The bT
is
the model to go for.

iii) The bT and cT perform relatively poorly in 15m mode rather
than their 16.6m (bT) and 17.6m (cT) modes, so competing in
15m mode is not recommended.

Any thoughts much appreciated.

Cheers,
Jim


I'll offer a few comments. My Ventus cT is a 1987 model and I've
got
about 1500 hrs on the ship over the past 13 years.

-- One possible reason for the apparently small number of C
models in
the US is that at least the early C's were brought into the US as
B
models, and then re-placarded as a C model. My '87 cT has the
original
B placard still in place, but X'd out with the new C placard
mounted
below it. I notice that a number of Ventus B models in the FAA
database are in fact C models whose owners never updated the
FAA
records.

-- I've got no complaints regarding the handling of the Ventus C,
thought I fly almost exclusively with the 17.6m tips. I've noticed
no
issues with handling with the 15m winglets, however.

-- Unfortunately I have never had to opportunity to fly a Ventus
B.

Originally Posted by Bob Gibbons[_2_]

On Tue, 17 Apr 2012 12:46:24 +0000, Jim Pengelly
wrote:

Hi everyone,

I fly a Discus bT at the moment and absolutely love it. However, I
am thinking of upgrading to a flapped turbo in the next one or two
seasons and the Ventus bT/cT would seem to be the natural
choice.

I have heard conflicting opinions about the various models:

i) The bT has handling issues and the cT was designed to
overcome these issues, with a bigger rudder and some other
changes. The cT is the model to go for.

ii) The cT has handling issues, can be difficult to bleed approach
energy due to the brake configuration and was not a popular
model, which is why there are so few of them around. The bT is
the model to go for.

iii) The bT and cT perform relatively poorly in 15m mode rather
than their 16.6m (bT) and 17.6m (cT) modes, so competing in
15m mode is not recommended.

Any thoughts much appreciated.

Cheers,
Jim


I'll offer a few comments. My Ventus cT is a 1987 model and I've got
about 1500 hrs on the ship over the past 13 years.

-- One possible reason for the apparently small number of C models in
the US is that at least the early C's were brought into the US as B
models, and then re-placarded as a C model. My '87 cT has the original
B placard still in place, but X'd out with the new C placard mounted
below it. I notice that a number of Ventus B models in the FAA
database are in fact C models whose owners never updated the FAA
records.

-- I've got no complaints regarding the handling of the Ventus C,
thought I fly almost exclusively with the 17.6m tips. I've noticed no
issues with handling with the 15m winglets, however.

-- Unfortunately I have never had to opportunity to fly a Ventus B.
The only unbiased comment I can quote is from Derek Piggott in the Dec
1992 / Jan 1993 Sailplane & Gliding issue.

"Whereas the earlier model has rather a reputation for stalling and
spinning if flown carelessly. the C model seemed a model of docility.
I frequently pulled into steep thermalling turns, getting down to well
below 40kt with only an obvious buffeting and sinking feeling clearly
indicating that this was far too slow. It did not once drop a wing
requiring any proper stall recovery. In spite of the extra wing span,
the rate of roll is excellent at all speeds and it is easy to fly
accurately rolling into and out of turns"

-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first. For my weight and 28
gal of water, I hit max gross just before I hit the non-lifting limit.
Bottom line, with the engine in place and ballasted to max gross, you
are at the same loading as without the engine, but you cannot dump
down to the same low loading as without the engine. With the engine
in, I can go from 10.1 lbs/ft2 max down to 7.9 lbs/ft2 min. Without
the engine, W/L ranges from the same 10.1 lbs/ft2 down to 7.2 lbs/ft2
(all with 17.6m span). The B model has the same issue and limitations.

-- For what its worth, only the C models were factory certified with
the 17.6m tips.

-- Regarding the air brakes, I have never found a situation where
landing flap and full dive brakes were inadaqute. That said, they
probably are not the equal of a PIK 20B or any other ship with full
90deg flaps (I've got about 2500 hrs in a 20B, before the Ventus).

Hope this helps your decision.

Bob

Every Ventus cT manual that I have looked at says the max weight with the engine in is 430 kg regardless of the span. With the engine out, 500kg at 16.6. and 17.6m respectively

Cheers
Colin

On Fri, 20 Apr 2012 02:59:15 +0000, Ventus_a
wrote:

'Bob Gibbons[_2_ Wrote:
.... text deleted

-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first. For my weight and 28
gal of water, I hit max gross just before I hit the non-lifting limit.
Bottom line, with the engine in place and ballasted to max gross, you
are at the same loading as without the engine, but you cannot dump
down to the same low loading as without the engine. With the engine
in, I can go from 10.1 lbs/ft2 max down to 7.9 lbs/ft2 min. Without
the engine, W/L ranges from the same 10.1 lbs/ft2 down to 7.2 lbs/ft2
(all with 17.6m span). The B model has the same issue and limitations.



Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

On Saturday, April 21, 2012 at 12:26:44 PM UTC+12, Bob Gibbons wrote:


Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

Sorry, but I'm still confused.

To my mind, a non-lifting limit is a hard limit, defined by the mechanical limit of the four wing-root pins. If you remove the engine (and fuel tank and engine battery) then this limit should not change; you've taken weight off the pins so can add more pilot weight etc. (ignoring balance considerations for the moment).

What the flight namual seems to be implying (and thanks, Colin, for the discussions) is that there are some wing bending issues. The (non-turbo) Ventus was designed for a MAUW of 500kg and the wing will cope fine with a max non-lifting weight of 255kg (for example - it varies depending on the model). What the manual seems to be implying is that SH then wanted to put a turbo in but came up against the (true) load limit of the wing pins, as well as some bending moment limitations on the wing, but the market need for a turbo version was great so they put a 430kg limitation on the MAUW.

I know that there are cT/bT pilots out there who ignore the 430kg limit and ballast up to 500kg with no issues. I'm asking the Collective Wisdom of y'all whether:
a) my reasoning above is correct;
b) whether to take the numbers in the flight manual with a grain of salt, bearing in mind the discussions with Herr Holigaus; and
c) whether it's worth asking SH to revise the flight manual to clear up the confusion; or
d) to obey the flight manual at all times and loads.

Answers on a postcard...

DH
TX

Originally Posted by David Hirst

On Saturday, April 21, 2012 at 12:26:44 PM UTC+12, Bob Gibbons wrote:


Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

Sorry, but I'm still confused.

To my mind, a non-lifting limit is a hard limit, defined by the mechanical limit of the four wing-root pins. If you remove the engine (and fuel tank and engine battery) then this limit should not change; you've taken weight off the pins so can add more pilot weight etc. (ignoring balance considerations for the moment).

What the flight namual seems to be implying (and thanks, Colin, for the discussions) is that there are some wing bending issues. The (non-turbo) Ventus was designed for a MAUW of 500kg and the wing will cope fine with a max non-lifting weight of 255kg (for example - it varies depending on the model). What the manual seems to be implying is that SH then wanted to put a turbo in but came up against the (true) load limit of the wing pins, as well as some bending moment limitations on the wing, but the market need for a turbo version was great so they put a 430kg limitation on the MAUW.

I know that there are cT/bT pilots out there who ignore the 430kg limit and ballast up to 500kg with no issues. I'm asking the Collective Wisdom of y'all whether:
a) my reasoning above is correct;
b) whether to take the numbers in the flight manual with a grain of salt, bearing in mind the discussions with Herr Holigaus; and
c) whether it's worth asking SH to revise the flight manual to clear up the confusion; or
d) to obey the flight manual at all times and loads.

Answers on a postcard...

DH
TX

Hi David

Too cheap to use a postcard but may I suggest a talk with Pat re his experience with OP if you haven't already. I'm sure he can add something

:-) Colin

At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine then
it should be a piece of cake to get there *with* the engine.

PF

If pilot + other non-lifting parts exceeds 255kg, then you can't fly. If
you can fly, then you can water up to the 500kg limit.

Indeed, it should be beneficial as water in the wings reduces wing root
bending. It increses bending at the end of the tank area, but the
manufacturer should have taken care of that.........

At 08:43 20 April 2012, Peter F wrote:
At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine
then
it should be a piece of cake to get there *with* the engine.

PF

On Apr 20, 2:56*am, Peter Purdie wrote:
If pilot + other non-lifting parts exceeds 255kg, then you can't fly. *If
you can fly, then you can water up to the 500kg limit.

Indeed, it should be beneficial as water in the wings reduces wing root
bending. *It increses bending at the end of the tank area, but the
manufacturer should have taken care of that.........

At 08:43 20 April 2012, Peter F wrote:



At 03:36 18 April 2012, Bob Gibbons wrote:
-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first.

You've lost me somewhere.

Why does pilot weight stop you getting to max gross as long as the wing
tanks are big enough?

Assuming tanks *are* big enough to get to max gross without the engine
then
it should be a piece of cake to get there *with* the engine.

PF- Hide quoted text -

- Show quoted text -

The Ventus (and nearly all gliders out there) fuselage is hanging from
the wings by four pins. On the Ventus they are about 15-20 mm in
diameter. The non-lifting weight limit is the maximum load those pins
can support and is unchanged by the extra weight water ballast adds.

Yes I know what max weight of non-lifting parts is.

If you can fly at all, you can fly at max gross.

I'm just confused by Bob Gibbons post (See quote below)

For his weight the margin on non-lifting limit is the same with or without
water the 28gals is irrelevant.

PF

Quote

-- Max gross with or without the engine is 500kg. The issue with the
engine in place is the 255kg non-lifting limit. With the engine in
place, the pilot weight determines whether the max gross of 500kg or
the non-lifting limit of 255kg kicks in first. For my weight and 28
gal of water, I hit max gross just before I hit the non-lifting limit.

End Quote