Experience towing a Grob-103 with a 160HP tow Plane?

[[email protected]]

Does anyone have experience with towing a Grob 103 or similar large 2-seat glider with a tow plane in the 160 HP class. Any specific experience details, lessons learned, or recommendations are appreciated. Did you do any testing prior to conducting training? If so, what was executed and logic for a testing progression, for instance. Does anyone propose environmental limits or runway length recommendations?

Asking because our 235 HP Pawnee is going to be offline for a while and we're investigating a lesser-powered Pawnee as a stand-in.

[Martin Gregorie[_6_]]

On Tue, 16 Mar 2021 12:40:05 -0700, wrote:

> Does anyone have experience with towing a Grob 103 or similar large
> 2-seat glider with a tow plane in the 160 HP class.
>
Yes, I've had a few tows at another UK club in their G.103 Acro III
behind their 150 HP Pawnee. That wasn't a lot of fun on a hot summer
afternoon in the Border country, a bit south of Edinburgh, because the
climb rate was almost nonexistent until the Pawnee eventually picked up a
few knots and was able to climb away, but still quite slowly. The G.103
got off ground in a reasonable distance, but I'd be surprised if we were
at more than 100 ft as we crossed the airfield boundary. Put it this way:
the ground looked closer than I liked for the next minute or two. This
was operating off a large, grass airfield, used for training RAF Typhoon
(heavy fighter) pilots in WW2. On that first visit my first flight was an
introduction to show me the airfield and surroundings, so we were flying
two-up, neither of us being heavy pilots. I got to fly the G.103 again,
this time solo, in the late afternoon.

I subsequently took my Libelle back to the same airfield another couple
of times, both in late October with cooler autumnal air getting quite
cold early to mid morning or late afternoon. On those trips that Pawnee
was able to do quite a bit better with the G.103 (flown two-up for
intrucuctory flights looking for wave and being shown the routes to and
from the local hill. Needless to say that Pawnee was a lot more sprightly
with my Libelle on the back.

I hope the above is useful info.


=====

I think the only slower aero tow I've experienced was two-up in a Duo
behind a 160 hp SuperCub at Wiener Neustadt, the huge grass Austrian
airfield to the south of Vienna. In that case I wouldn't care to say
which aircraft left the ground first - only that the run seemed rather
long!


--
Martin | martin at
Gregorie | gregorie dot org

[Hank Nixon]

On Tuesday, March 16, 2021 at 3:40:07 PM UTC-4, wrote:
> Does anyone have experience with towing a Grob 103 or similar large 2-seat glider with a tow plane in the 160 HP class. Any specific experience details, lessons learned, or recommendations are appreciated. Did you do any testing prior to conducting training? If so, what was executed and logic for a testing progression, for instance. Does anyone propose environmental limits or runway length recommendations?
>
> Asking because our 235 HP Pawnee is going to be offline for a while and we're investigating a lesser-powered Pawnee as a stand-in.

We tow our ASK-21 with our 160 Super Cub. We pull it back a bit more that when we pull with our 180 Pawnee. Both do well enough to be safe.
UH

[[email protected]]

For many years my last club regularly towed our 103 with a 150hp Super Cub without issues. Grass strip, not particularly long but no obstructions at either end. We only had to watch when the field was soft. That said, the climb out off the end of the runway was not very impressive. Good tow pilots learn to use finesse when hp is lacking. Things like lifting one wheel first to pick up speed, staying in ground effect as you accelerate and sometimes using flaps momentarily to pop the towplane off the ground when it just doesn’t want to break free!

My current club uses a 150 hp Citabria pulling at most a Puchacz (lighter than a 103) and a Perkoz. Again, no issues for the most part but marginal when the field is soft. I’ve done plenty of towing at both clubs and I would say the Super Cub does more with 150hp than the identically-powered Citabria so it is not just hp that matters.

As for tow pilot training in these circumstances, you just have to make sure the pilot is comfortable with his/her abilities. I have to admit that we have continued many tows on faith believing that we would eventually get off and clear the bushes or fences simply because we have always managed to do so. Any pilot flying by the numbers would in many cases have abandoned some of the tows we do! That said, we’re looking for a new towplane with more hp!

On Tuesday, March 16, 2021 at 3:40:07 PM UTC-4, wrote:
> Does anyone have experience with towing a Grob 103 or similar large 2-seat glider with a tow plane in the 160 HP class. Any specific experience details, lessons learned, or recommendations are appreciated. Did you do any testing prior to conducting training? If so, what was executed and logic for a testing progression, for instance. Does anyone propose environmental limits or runway length recommendations?
>
> Asking because our 235 HP Pawnee is going to be offline for a while and we're investigating a lesser-powered Pawnee as a stand-in.

[Mark Mocho]

When giving these examples, you should include field altitude and density altitude to give us an idea of what was actually happening. At out field elevation (6,200 MSL) and a density altitude often over 9,000 in the summer, I suspect a 160 HP towplane with two occupants in a G-103 would only be doing taxi tests.

[Martin Gregorie[_6_]]

On Tue, 16 Mar 2021 21:12:10 +0000, Martin Gregorie wrote:

> Yes, I've had a few tows at another UK club in their G.103 Acro III
> behind their 150 HP Pawnee.
>
40m (130 ft) AMSL (altitude from GE).


--
Martin | martin at
Gregorie | gregorie dot org

[[email protected]]

On Tuesday, March 16, 2021 at 5:37:37 PM UTC-4, Mark Mocho wrote:
> When giving these examples, you should include field altitude and density altitude to give us an idea of what was actually happening. At out field elevation (6,200 MSL) and a density altitude often over 9,000 in the summer, I suspect a 160 HP towplane with two occupants in a G-103 would only be doing taxi tests.

I have made several hundred tows in the 180 hp Pawnee with a 103 and ASK21, no problem! If I had my choice the 180 hp Pawnee would be my favorite.

[Dan Marotta]

Decades ago, I towed all comers, including G-103, Twin Astir, and Blanik
with a 180 hp Super Cub and a 180 hp Citabria at Black Forest, elevation
7,050 and with density altitudes aroun 10,000'. We had a 3,400' runway
with a fence at the end of the normal direction. IIRC, it rarely took
more than half of the runway.

Dan
5J

On 3/16/21 3:37 PM, Mark Mocho wrote:
> When giving these examples, you should include field altitude and density altitude to give us an idea of what was actually happening. At out field elevation (6,200 MSL) and a density altitude often over 9,000 in the summer, I suspect a 160 HP towplane with two occupants in a G-103 would only be doing taxi tests.
>

[[email protected]]

Good point. 1500’ MSL.

On Tuesday, March 16, 2021 at 5:37:37 PM UTC-4, Mark Mocho wrote:
> When giving these examples, you should include field altitude and density altitude to give us an idea of what was actually happening. At out field elevation (6,200 MSL) and a density altitude often over 9,000 in the summer, I suspect a 160 HP towplane with two occupants in a G-103 would only be doing taxi tests.

[Roy E]

On Tuesday, March 16, 2021 at 1:40:07 PM UTC-6, wrote:
> Does anyone have experience with towing a Grob 103 or similar large 2-seat glider with a tow plane in the 160 HP class. Any specific experience details, lessons learned, or recommendations are appreciated. Did you do any testing prior to conducting training? If so, what was executed and logic for a testing progression, for instance. Does anyone propose environmental limits or runway length recommendations?
>
> Asking because our 235 HP Pawnee is going to be offline for a while and we're investigating a lesser-powered Pawnee as a stand-in.

We tried it once about twenty ears ago with our 150 hp Cessna 150, on a 2500 ft long grass strip at 1900' asl at about 70 degF with a light breeze. The tug had gained about 1 foot of altitude at the end of the runway. To shorten the agony on tow, the glider released below 2,000 ft agl. Our chief tow pilot took a long rest after that tow. We never tried it again.
We still have the Cessna 150/150 and perform 2,000 ft tows with our L23 in about 10 to 12 minutes, start to stop. Our club has ruled out the purchase of a Grob 103, because of the memory of that one tow.
Roy

[Marton KSz]

I've been towed once by a 150HP 7KCAB Citabria (in a Grob 103a) starting from sea level, there was no drama, although the climb was a bit shallow.
We've been towing Blaniks and PW-6 regularly with a 160HP Super Cub, no issues below 6000ft (western WA).

[[email protected]]

The 150hp 7GCBC has less of an issue. The longer wing and flaps help. Again, it’s not just hp that matters. I’ve towed behind 180hp Scouts that were dogs because the extra hp is wasted with a heavier airframe and I suspect a poor prop choice.

On Wednesday, March 17, 2021 at 2:17:17 AM UTC-4, Marton KSz wrote:
> I've been towed once by a 150HP 7KCAB Citabria (in a Grob 103a) starting from sea level, there was no drama, although the climb was a bit shallow.
> We've been towing Blaniks and PW-6 regularly with a 160HP Super Cub, no issues below 6000ft (western WA).

[Dave Nadler]

On 3/16/2021 3:40 PM, wrote:
> Does anyone have experience with towing a Grob 103 or similar large 2-seat glider with a tow plane in the 160 HP class. Any specific experience details, lessons learned, or recommendations are appreciated. Did you do any testing prior to conducting training? If so, what was executed and logic for a testing progression, for instance. Does anyone propose environmental limits or runway length recommendations?
>
> Asking because our 235 HP Pawnee is going to be offline for a while and we're investigating a lesser-powered Pawnee as a stand-in.

I suspect you won't get too many replies from those who have tried it.
Why?
They are still on tow...

[Nicholas Kennedy]

When I started flying Parowan Ut the tug there was a C150/150 hp.
The tow pilot was this skilled gentleman named Gene.
The Density altitude in the summer could go up to 8-9 K easy.
I launched my fully ballasted ASw 20 there with that tug many, many times.
Parowan is open ground , not much in the way of obstacles to clear.
I gave quite a few rides there with that tug in a L-13.
While it worked Ok and was cheap to run, it helped alot to have 2 skilled pilots on the rope.
Then a 600 HP biplane Ag Wagon thing showed up. Super expensive to run but very short time on tow with that thing. Unfortunate to report that plane was quickly balled up in short order.
Back to the C150/150. For years.
We also gave a couple thousand rides here in Telluride with a C150/180. Density here in the summer goes over 12k.
That plane was also cheap to run.
You can tow, on fairly low HP, just need some nerve once in a while if you launch into a sinker.
If you have obstacles to clear, that's a whole different situation than Parowan and Telluride.
Nick
T

[Jim S]

No experience with a Grob 103 but I tow with a short wing Piper 160hp. I could not tow a maxed 103 (1400 lbs?) due to a 1200 lb limit on the Piper’s tow hitch.
Last Summer, density altitude 3 to 4000’ , towing a maxed out 2-33, 220lb tow pilot and 30 gallons of fuel yielded about 300/350 fpm. Not stellar but completely safe as we departed from a paved surface.
Our tow plane is a PA22-108 with no interior and an stc’d O-320-B2A.. Weighs 1010 lbs empty. It is an extremely cost effective tug. We want to purchase a PW6 later this year and our intention is to continue to use the PA22 as our tug. The limit on the tow hitch and gross weight on the PW6 are matched. I suspect the PW6 will tow more easily than the 2-33 due to lower drag.

[Ron Clark[_2_]]

Jim S,

Thread drift notwithstanding, if you haven't already installed them, a vortex generator kit really helps with low speed handling on the short winged Colt. It's a pretty cheap and easy performance enhancement for towing gliders.

RC

[Jim S]

Hi Ron,
Ironic you brought that up.
Currently, I am building a new set of wings for the PA22. I am planning on installing VGs. At the moment, fabrication of the Stewart square wingtips are in process. These are not drooped but extend the full airfoil shape the entire span. There is a small increase in wing area but primarily gets rid of the round tapering wingtip. Also, the cover will be poly-fiber as it is light compared to dope. My current wings have a thick coat of two part Aerothane and consequently heavier than they need to be. The new lighter wings, extended tips and VGs should make this tug even better.