View Full Version : Warbird Q: Bf109 leading edge automatic slots

28th Aug 2001, 20:32
Does anyone know how these worked? Specifically, what made them move and what was the mechanism which decided when to deploy/retract them?


28th Aug 2001, 23:44
to my knowledge they were simply slotted and hung freely in a 'deployed' position until the airflow was sufficient to push them against the leading edge. no real mechanism involved and no way of controlling them in the cockpit...apparently quite an issue as they had a habit of deploying one before the other- not the best arrangement in a vertical scissors i'd say

29th Aug 2001, 00:15
Automatic slats have been quite common. A couple of early biplanes had them (?Tiger Moth? but I could be wrong) and I think even the A4 Skyhawk of Vietnam vintage had them too.

One of those rare principles of flight that actually help the pilot without him needing to do anything!


29th Aug 2001, 02:50
thank you. Springloaded rather than affected only by aerodynamical forces I guess as they are deployed when on the ground IIRC?

I'm asking since I find the skill, cunning, craftmanship and sheer bloodymindedness of the people who truly knew how to develop control surfaces without running it all through CFD simulations amazing.


Tiger_ Moth
29th Aug 2001, 03:01
Yeah, Tiger Moths have automatically deployed slats which deploy when your speed gets around 45 or something. You can lock them from inside though and often do if its windy or something.

A and C
29th Aug 2001, 12:28
The slats are normaly held in by the airflow but as the A of A increasese the C of P moves forward and the stagnation point ahead of the wing tends to move down and under the leading edge it is this high pressure air under the slat and the drop in pressure above the slat as a result of the C of P moving forward that deploys the slat just at the time when the boundary layer needs re energizing to avoid the airflow seperating from the upper surface of the wing thus increasing the A of A is which flow seperation happens =lower stall speed.

29th Aug 2001, 14:46
Aaaah, of course. I had a feeling it was something smart and simple. :) We could probably (re)learn a lot by studying older designs a bit.


Flight Safety
29th Aug 2001, 23:05
If memory serves, the old Saberliner biz jets also have this same type of slats. Spring pressure extended, and stowed by air pressure in flight.

Kerosene Kraut
30th Aug 2001, 16:40
Me-108 had similar devices. German Astronaut Furrer crashed one over Berlin-Johannistal some years ago. While performing unauthorized aerobatics he ripped off the slats and lost control.

Stein Meum
30th Aug 2001, 22:18
Yes, both the Sabreliner and the F-86 Sabrejet had automatic slats working w/o pilot action.They were interconnected so they deployed simultaneously,whereas the Messerschmidt design operated independently.If you did not fly the ME in perfect co-ordination,one slat could deploy before the other and throw your aim wide of the target.Top ME aces were real "Experten"!

2nd Sep 2001, 18:11
Well set up slats on Bf 109 will deploy so easily that just finger tip pressure (on the ground of course, part of the pre flight) will move them out.Any binding, clear it!!
Re. the DH 82, use the lever to stow the slats before doing aeros, otherwise it can ruine your whole day.
Cheers all.