Grob 109

Do they still make the G-109? Anyone seriously considering this type of
aircraft should also take a look at Pipistrel and Phoenix.

Dan Marotta

On 10/12/2014 7:39 AM, wrote:
I have flown and instructed in both the A and B models and also flown the A with the L2400(non turbo) engine and constant speed propeller. One big advantage of the B is that the wings can be folded and hung off the fin allowing it to fit in a 40ft container. Personally I think the A with the L2400 is the best option. The extra horsepower and wobbly prop mean the Take off run is reduced and climb rate and cruise are significantly better than the standard 109A and on a par with the B if not a little better. The bubble canopy is much better than the B arrangement as in a right hand thermal you cannot see into the turn very well in the B which is a little frustrating in a busy thermal. Both have benign stalls around 40kt and tend to mush rather than break unless at very high angles of attack, much better than tne H36 Dimona which drops the left wing consistently (this was one of the reasons the RAF bought the 109 rather than the Dimona) economic cruise seems to be around 85kts using 11-12 litres an hour regardless of the model and the L2400 and the B will cruise around 110kt burning 15l per hour. Handling is turgid and stodgy in all models rather than crisp compared with the dimona or the IS28 which is the best handling motorglider i have flown. The Schempp airbrakes are very powerful compared with any other motorglider out there and give a nose down pitch when opened. Approaches flown like a glass two seater but at 55-60kt work well using the airbrake as you would in a glider remembering to flare just a little higher because of the undercarriage. Two potential gottchas are 1. Flying from the right seat means left hand stick right hand airbrake which is uncomfortable for glider pilots and has resulted in a number of broken grobs. Power pilots cope better with this but need to get usedto the powerful airbrakes as opposed to flaps. 2. Don't land pulling excessively on the air brakes as the wheel brake is the last part of the travel and you can stand the aircraft on its nose this way. On the other hand its also possible to stand it on its nose with the toe brakes or ground loop and brake the tail. I find the best technique is to land with 1/2 to 2/3 airbrakes and then EASE the brakes on on the ground using the wheel brake lever. I only use toe brakes to keepitstraight in a very strong crosswind or manoeuvring on the ground.

A word about takeoff techniques. Motorgliders have marginal power and the best way is to make the wing do the work not the engine. As a taildragger on takeoff the wing is presenting a high angle of attack and is very draggy so a neutral stick or stick back takeoff prolongs the ground run. Stick forward to get the tail up and reduce the angle of attack and drag allows tne aircraft to accelerate faster and then you can "ease" it off when she is ready to fly. Obviously you have to be ready to catch the swing when the tail comes up and in a strong crosswind you might need a gentle dab of toe brake to hold it straight. Again wherever possible I will angle across a runway or strip on take off and landing to maximise the into wind component. In the cruise climb if you allow the aircraft to accelerate it will then start to climb gently this is a better option than raising the nose like a normal aircraft which just increases the drag and speed will bleed in the climb. The aircraft isn't particularly prone to icing but the carb heat is there for a reason. I always pull it while the engine is in cruise power before closing the throttle for a descent to get a big blast of hot air into the carbs. The cabin air choke and carb heat are all the same shape and grouped together on the pannel so its easy to grab the wrong one in a hurry. If you can change the shape of them or colour code them it helps. When air starting the engine its better to start on the ignition than air start in fine pitch as the engine will scream round to the red line at the 75-80kts required to get the prop spinning which is not a great way to treat a cold soaked engine. Obviously turn off as much power when soaring engine off and feather the prop 50kts seems to work ok in thermal turns and the thicker A wing profile seems to have the edge on the B for soaring. Be careful not to turn the key to park when soaring or the key can fall out and bugger off out of reach (don't ask me how i know). Unfeathering starting and increasing power to stop a descent takes about 200ft in grobs with the 3 position prop.If its an electric constant speed unit this can take MUCH longer to unfeather and upto 500ft can be lost even in still air. Also remember in fine pitch throttle closed you have an airbrake effect from the prop. On that note you will only try a course pitch takeoff once unless you have over 500M TORA and nothing in the way!!! If roll gets excessive at taxi better to stop and start again. A slightly faster taxi speed might help. Remember to taxi into wind stick back downwind stick forward and try not to use power against brake to turn, especially if turning out of the wind you can stand it on its nose. Be ready to catch the tail coming up if taxiing over a lip from one surface to another or if you hit a rut or pothole
One final point I always suggest turning off the master then the ignition unless youneed the radios at shutdown. This way you know you have left a dead aircraft and will not result in returning to a flat battery.
Most people dismiss motorgliders as not real aircraft but a grob will do pretty much anything a 150 or 152 can more efficiently, and they require a real feel and some skill to get the best out of them which can make them very rewarding aircraft to fly.

I purchased a 109B in the late 80's and formed a consortium of eight pilots to own and operate it. I was the check pilot and instructor for the group and I developed a low opinion of the design for many pilots. It is a complex little airplane. It is a true taildragger and has a Mickey mouse shifting mechanism to transition from cruise to climb and visa versa. It will not climb in the cruise setting and if you inadvertently miss the shift on downwind you will not be able to go around. I had students do this a few times fortunately with enough runway to roll out and taxi back. The single ignition version is prone to plug fowling, which happened to me twice on cross country flights necessitating finding an airport quickly. It took me 30 hours of instruction to ready one of the members to safely operate the aircraft, and he was both a licensed power and glider pilot.

I sold my share in about 1993 and the new member ( I did not check out) was overflying his vacation home in central Oregon and was unable to climb away and crashed with the engine at full power. I think they concluded it spun in. He probably missed the shift into climb mode. Neither the 109 or the pilot survived.
The 109B is a busy, underpowered aircraft. (neither beast nor fowl) and if the A is even worse It would probably be a poor option.

Having said that, I had a lot of fun in the airplane. I flew it from Tennessee to Oregon and up and down the west coast a few times, I just don't think it is for everyone. .
Dale Bush

I have owned a G109B for 30 years, initially as a syndicate and now as sole owner. Although I agree with much that has posted, I do not share his conclusions. (I expect you will say "of course").

Here is re re-post from earlier in this thread:

"The wing section is much thicker on the 109A, and pretty poor IMHO.
The A will spin of a 50kt turn, and don't ever think of attempting a
take-off with water on the wings. I saw one go through the upwind
boundary because the under surface got wet from long grass during taxying.
It has a 2 litre Limbach engine, while the 109B has 2.5 litre."

My G109B has been used primarily for soaring (3800 aiframe hours / 1850 engine) and has motored to the European Alps on 17 occasions, where the conditions are rather better than in the UK. Having said that, it has done 100 hours for 20 engine in most recent years in UK.

I have never spun off a turn, even thermalling down to 42 kts. It could do with a bit more rudder power to overcome the adverse yaw at high roll rates, making it reluctant to turn, but a chunk of opposite aileron gets the turn going nicely once the desired bank angle is achieved.

I mostly "bump start" the engine when preparing to land, but the best technique is to dive to 80kts while exercising the prop between feathered and coarse to find the sweet spot.

My model does not have the wheel brakes activated by the airbrakes, being a later mod-state (post Sno. 6340), but although the toe brakes are very effective you would be hard pressed to get the tail up, especially on grass.

My one-man wing folding attachment means I can store it in its shed after every flight. The time taken to do this is the same as that required to fit wing and fuselage covers, making it the best option.