Tiger Moth auto-slats

[Centaurus]

Tiger Moths came with slats on the upper wing that extended when the wing was close to the stall. They could be locked closed by means of a lever in the cockpit and were locked in the shut position for taxiing over rough ground and for aerobatics and spinning.

I recently went for a ride as a passenger in a privately-owned Tiger Moth that had the slats removed. Seems it cost money to service the slats and the owner (a current airline captain) decided the slats were useless anyway.

The Pilot's Notes Tiger Moth (RAF version) assumed the slats were operative for take off and landing and I guess the recommended take off and approach IAS of 58 Knots was based on this.

Question: Do the slats either removed or locked change the flying characteristics of a Tiger Moth and if removed how does this affect the airworthiness of the aircraft?

[Ex FSO GRIFFO]

G'day Mr C,
Taxing the old memory a little here, but many years ago I used to instruct on Tigers in the WA wheatbelt, and have to qualify this by saying I have never flown with the slats actually removed.....
However, when 'playing with' the aircraft at altitude trying to see what it would / would not 'do', and check it out for 'rigging', it was quite normal to see the slats start to open when approaching stall configurations. Magic!
Although I do not recall actually feeling anything too different, I would always look up to see if the slats were still 'in', or starting to work, or even fully extended, and try to 'feel' the acft.
A visual stall warning device if you like - although they often fully deployed with little or no apparent 'feedback' thru the controls, the sight of them 'fully out' was a warning. The control column / rudder were fairly 'mushy' at this point anyway, so you knew not to do anything silly close to the ground.
They were always 'unlocked' for take-off / ldg, as they were supposed to delay the stall over the upper mainplanes and provide that much 'safety factor'. I never had a 'bad' landing in one - so I suppose they must have worked OK.
I guess if the man is aware of the limitations of his machine, and how it 'feels'..........
I mean, we have all landed 'flapless' from time to time.....???
And, we just fly the aircraft accordingly......

Does this help?:ok:

[Confabulous]

Did he have the autoslats removed and a fixed LE section put in it's place? I would have thought that permanently locking the slats would be easier :uhoh:

[foxmoth]

Some Tigers that were never inthe services never had slats, you wil often find this goes with no spin strakes. Lack of slats makes a minor difference in the stall (about 2kts and slightly more "break").

[Wwyvern]

I trained on Tiger Moths (note - I didn't say I learned to fly on Tigers; I'm still learning after nearly 50 years). I note in my logbook that I did a solo spinning detail after 9hrs50mins dual and 8hrs50mins solo.

What sticks in my memory is that I was so "concentrated" on the spinning exercise that my first attempts at putting the aircraft into a spin came to naught because I forgot to lock the slats. Once this oversight was sorted, she spun like a dream.

All of our Tigers had slats, so I have no experience of flying without them.

[asw28-866]

As a commercial Tiger Moth Pilot, I can tell you that the slats are a real pain. The cables used to operate them stretch over time, especially if one is doing a lot of aeros allowing the slats to 'float'. This stresses both the slat mechanism and the wing, leading to all manner of maintenance headaches. We remove the slats as a matter of routine whenever we are having wings rebuilt.

They make practically no difference to the approach/landing in a Tiger, do prevent a wing break at the stall, which is very benign anyway. But otherwise serve no useful purpose.

My understanding is that they were an extra charge option on the civilian aircraft, but were specified as standard on the RAF ones?

regards

866

[PeterX60]

When aerotowing with a Thruxton Jackaroo (4-seat Tiger conversion) and with 'vintage' gliders on the other end of the rope, they were happiest if the airspeed was kept down to 'slat pop' speed. They were a very effective max alpha indicator.

[Centaurus]

Thanks for replies so far. asw 28-866 - If the slat cables stretched over time and caused the "floating" you describe, this suggests routine maintenance of the cables was lacking - not faulty cables. Most components, if not serviced to manufacturer's specified time limits will inevitably cause problems down the line. While the IAS stalling speed difference may be negligable, the CAS stalling speed is what counts. There is no doubt the slats act as an effective stall warning device.

Removal of a component for reason of servicing costs can lead to undesirable results. In 1992, a Tiger Moth spun in during the execution of a simulated engine failure shortly after take off at 300 ft. One pilot was killed. The accident investigation board criticised the operator for locking the slats in the permanently closed position (to save the bother and costs of servicing). Litigation quickly followed.

The Board of Inquiry stated the accident might have been avoided if the slats had been operating as they served as an effective signal of stall warning and a slower stall speed.

[asw28-866]

Centaurus, of course I did not mean to imply a lack of maintenance, rather at our utilisation rates, the cable issues required increased maintenance and downtime, not good for a commercial operation.

We have had, and continue to have zero issues with operation sans the slats. I find the moth benign in stalling charateristics compared to the over 85 types I have flown as P1 without the slats.

In high utilisation aircraft, without the beneift of an Air Force maintenance regime, no slats is the way to go.

866

[barit1]

With the few degrees sweepback, I should imagine the TM does brisk snap rolls :ooh:

Or do the slats "tame" this behavior? :confused:

[tinpis]

"Brisk" is not a word you would associate with a Tiger.
I can never recall flying one with operable slats most had spin strakes tho.
I often wondered why ailerons were fitted :p

[Centaurus]

Tinpis. Wash your mouth out. Ever tried flying on instruments in the Tiger? That's where the original "under the hood" expression came about because of the canvas hood completely enclosing the student. Impossible to cheat. Line up for take off on all-over grass field - full throttle - keep straight using large turn and skid indicator. If it showed rate four turn you had already ground looped. It was a classic limited panel flying as there was no AH.

[pulse1]

I got my PPL on a Tiger which had the slats removed. I do not remember being briefed about any special problems.

[boredpilot]

I've never flown a Tiger with the slats removed, but have been flying Tigers for a while & find that if you lock them after t/o and leave them there until the d/w checks there's nothing to worry about. I think one of the reasons the cable goes slack is if you taxi with them unlocked and they bank about.

The best thing I find is when sitting in the front seat (during checkouts for example), you can see them pop out in your peripheral vision (said the bishop...) , which means the speed is getting a bit low - a good reference on the approach.

Other than that I would wonder what the point was for a quoted 2kt diff at the stall - was the original ASI ever that accurate????

[foxmoth]

With the few degrees sweepback, I should imagine the TM does brisk snap rolls

Or do the slats "tame" this behavior?

Slats should be locked for Aeros so will not affect, flick roll is OK but hardly "brisk".;)

[gaxan]

Some Tigers never had them fitted, some Tigers do.The Queen Bee has them but without any means of locking them. To be honest, I am not sure why de havilland bothered !

[On-MarkBob]

The only time that the slats were any good were in tight turns pulling 'G', and one day they even saved my life and I am forever grateful for them. I was glider towing and coming in fast after a tow. The field was by a hill and the wind 'on the hill'. The approach thus was to turn in front of the hill to land into wind. I raked the tiger into a steep low turn by the hill to turn into wind and ran out of elevator, I was going to hit the hill. Then suddenly the slats popped out and gave me the extra elevator I needed to complete the turn. So now you know, yes they work!

Bob