Unable to keep nose down on 'Go Around'

[nomadpete]

I have read some contributions in one of these forums, which talk about Jabs developing a almost uncontrollable rising nose when doing a 'go around'. The description went something like this:

 

Landing with full flaps, and when full power applied to do a go around, the nose comes up and is very hard to keep level, and airspeed started to drop. One person reported actually having to reduce power in order to get the nose down.

 

One Answer:

 

The Jab has a very effective servo type trim system which relies on airspeed to get its power. The more airspeed, the greater the trim force. So the the trim, which was correct for the quiet descent, will suddenly give a strong nose up force as soon as the throttle is opened up. It is likely that the above 'problem' could be instantly corrected by reaching across and RETRIMMING.

 

Hopefully this will reassure those who have been worried.

 

PeterT

 

 

[Guest Qwerty]

Gday Pete

 

The trim system on a jab is actually just a weak spring attached to the elevator cable and is easily over-ridden by light pressure on the stick. The problem with the go round was caused by the engine. The particular model that does this is the SP6, a small, light airframe with 120 hp installed in it. The airfram/engine combination is awsome to fly but does have some idiosyncrasies, that is one of them, another is the torque roll which happens at the same time as the pitch up. The little turds also drops the right wing in a high power stall. I was expecting the left wing to go and the bugger snapped over to the right. Unfortunately I was ready and waiting to give it a big heap of right rudder so I was a bit slower than I wanted to be with my recovery.

 

Cheers, Qwerty

 

 

[Derby]

Hi Qwerty

 

I think you will find that the trim has it's own cable on Jabs

 

Rory

 

 

[Guest Qwerty]

Yes, I did find that. The trim cable operates a weak spring that is easily over ridden by pressure on the stick.

 

 

[Tomo]

Thanks very much for posting that info Peter... always good to have a bit more information up the sleeve.

 

 

[J170 Owner]

Hmmm, I have not experienced this with my J170. Maybe I'm not trimming properly on finals?

 

 

[winsor68]

The 170 I flew didn't have enough grunt to pull the wrapping off a soggy sandwich... lol

 

It is interesting that the bigger horsepower aircraft will do this... in ones mind one tends to associate more grunt with the opposite... I am guessing most people if they were to put an extra 40 hp in their aircraft would expect the opposite?

 

 

[facthunter]

Some pilots prefer to leave a little back stick pressure when the aircraft slows for "feel". High wing or underslung jet engines often want to go to high nose up positions on go around, due to the thrust line and drag relationship.

 

Springs are a crude mechanism but simple and cheap. A good aircraft will have moveable trim tab(s) which effectively enable an alternate method of pitch control if primary elevator control fails. A plane is generally unflyable when the elevator malfunctions, so it's nice to have a back-up.

 

I know, because I have had it happen. Nev

 

 

[djpacro]

.

 

 

[turboplanner]

Couple of things specific to the J170.

 

1. Trim setting. The cables are squashed together with control cables and trim can easily be pulled out of adjustment. At times you need one hand on the control and the other on the trim lever - nice for monkeys to fly, not us.

 

2. If you didn't forget to move the flaps to take off flap, you may be taking off too early. In the unergonomic Jab cockpit watching the electric servo indicator will distract you from flying, so counting the servo time can be better than watching the horrible little slide.

 

3. If you forgot to put the flaps up for the go round and you are on full flap, land if you have enough runway, or be prepared for a wild ride because the one big surface on J170's is the flap which acts like an air brake and the resultant forces will try to put you over on your back. Very heavy forward stick to get the nose down for some flying speed, and wait it out until there is enough altitude to bring the flaps up without sinking on to the runway or a fence.

 

 

[G-OMER]

I have had this on my 450UL. when learning to fly on my solos I did plenty of go arounds, the jab would always lift the nose right up and i was pulling back on the power to lower it. I found I had full fwd stick in and it still did it then on 1 go around i hit the trim lever and then i had plenty of fwd stick, so if i have to do a goaround now i instinctivly after power push the trim fully fwd then no probs, if i think i may have to do a go around when on finals i will put the trim to neutral then no problem, all this means is holding some back stick on.

 

on a normal landing i have the trim back, not fully, say a 1/4 of the way from neutral then the jab lands itself.

 

Cheers

 

Gary

 

 

[Tomo]

In Jabs I always take off neutral trim. In a go around stick goes forward with throttle, and trim as soon as you can. I find if you keep the nose down from the start and not let it get to high up it seems to work - I must say I haven't really done many go arounds recently in a Jab, but In J230's and the J120 that's my general procedure.

 

Couple of things specific to the J170.1. Trim setting. The cables are squashed together with control cables and trim can easily be pulled out of adjustment. At times you need one hand on the control and the other on the trim lever - nice for monkeys to fly, not us.

 

2. If you didn't forget to move the flaps to take off flap, you may be taking off too early. In the unergonomic Jab cockpit watching the electric servo indicator will distract you from flying, so counting the servo time can be better than watching the horrible little slide.

Don't think that's specific to just the J170 Tubz, nearly every aircraft I fly I have a hand on the control and use the other to move the trim...

 

Unergonomic...? At least the flap gauge is at eye level and moves, some of the C172M aircraft's flap gauge is pretty painful. You soon learn the 4 second, 2s and 2s system...

 

 

[turboplanner]

Yes Tommy but the trim lever doesn't usually depart the scene to a new position just because you move the controls.

 

What I meant was you have to use the second hand to correct the trim back to where you set it.

 

 

[Dieselten]

Don't use full flap for a go-around! Half-flap is plenty. If you are doing touch-and-goes, either use half-flap for approach and landing or get the flaps back to half before the aircraft unsticks on the next takeoff. Practice flapless landings too, especially if you have electric flaps - flap motors have been known to fail.

 

 

[G-OMER]

i had to do a go around when training, powered up etc and dropped the flaps to half, was at about 30ft up, slammed the jab into the run way and bounced back to 30 ft, wont do that again, to low and slow to go to half flap.

 

 

[turboplanner]

Don't use full flap for a go-around! Half-flap is plenty. If you are doing touch-and-goes, either use half-flap for approach and landing or get the flaps back to half before the aircraft unsticks on the next takeoff. Practice flapless landings too, especially if you have electric flaps - flap motors have been known to fail.

I don't know anyone who recommends full flap for a go round. The problem is HF - forgetting to select takeoff flap before the aircraft leaves the ground.

 

G-Omer's spelled out very clearly the penalty for trying to fix it by reducing flap.

 

The Jab electric flap is too sensitive, drops it too fast unless you use little flicks on the switch. In a Cherokee you can grab the flap lever and very slowly trade off flap without losing height, and the same pulling it on.

 

 

[G-OMER]

Don't use full flap for a go-around! Half-flap is plenty. If you are doing touch-and-goes, either use half-flap for approach and landing or get the flaps back to half before the aircraft unsticks on the next takeoff. Practice flapless landings too, especially if you have electric flaps - flap motors have been known to fail.

yes agree on intentional go arounds or touch n goes, but when not intentional your on full flap..