Gnat Roll Rate and that fuse.
Thread Starter
Join Date: Jun 2001
Location: England
Posts: 1,006
Likes: 0
Received 0 Likes
on
0 Posts
Gnat Roll Rate and that fuse.
I was looking at a Gnat the other day and remembered some comment on a program about the roll rate on the Gnat being increased if you took a certain fuse out.
Anyone know what this fuse did??
Anyone know what this fuse did??
Avoid imitations
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,573
Received 413 Likes
on
218 Posts
I think you'll find it slowed down the roll rate 
There was an electrical circuit in the Gnat whose purpose was to limit maximum aileron angle at high speed. The circuit was fused by (I think) 'Fuse 13'. A member of the Red Arrows realised that if the fuse was removed, full aileron and an exceptionally high 'twinkle' roll rate would be achievable. They tried it - it did indeed work...
However, 'the girls' (i.e. A squared E squared) were concerned about both inertial coupling and fin stress resulting from such violent rolls; their counsel prevailed and orders were issued that the Reds' fuses were to be re-fitted. But no-one had said that the fuses had to be replaced 'serviceable'.....
Sadly, a Gnat did lose its fin at low level after a twinkle roll and the crew were killed. The fuses were all replaced with serviceable ones.
However, 'the girls' (i.e. A squared E squared) were concerned about both inertial coupling and fin stress resulting from such violent rolls; their counsel prevailed and orders were issued that the Reds' fuses were to be re-fitted. But no-one had said that the fuses had to be replaced 'serviceable'.....
Sadly, a Gnat did lose its fin at low level after a twinkle roll and the crew were killed. The fuses were all replaced with serviceable ones.
Thread Starter
Join Date: Jun 2001
Location: England
Posts: 1,006
Likes: 0
Received 0 Likes
on
0 Posts
Beagle,
Thanks for the reply. How did the circuit work, did it engange some sort of gear to limit the aileron movement. Also, if you know,what speed did this kick in?
Shytorque, Thankyou for reminding me not to be so vague in my questions.
18
Thanks for the reply. How did the circuit work, did it engange some sort of gear to limit the aileron movement. Also, if you know,what speed did this kick in?
Shytorque, Thankyou for reminding me not to be so vague in my questions.
18
Join Date: Jun 2002
Location: Southern UK
Posts: 92
Likes: 0
Received 0 Likes
on
0 Posts
Beagle, your remarks and those of the TV programme that gets repeated every now and again are a vile calumny on the good name of Boscombe Down. The true story is as follows:-
There was indeed a Fuse 13 on the Gnat. This protected a circuit which restricted the aileron travel to 12 degrees when the U/C was retracted while allowing the full travel of 15 degrees when it was down. This protected the wing and aileron from overstress at high speed while permitting full aileron for manoeuvrability in the circuit. With Fuse 13 fitted and serviceable the aircraft was cleared to rapid roll (full lateral stick, fast as you like) up to about 500 knots and 5g. The Red Arrows realised that they could roll faster with Fuse 13 removed, but far from acting irresponsibly they asked Boscombe if they could rapid roll with it removed if they kept to a more restricted flight envelope. This was investigated with the Design Authority and it was determined that they would be OK if they stuck to 1g rolls at no more than 350 knots. They were happy with this and a proper clearance was issued. The Arrows used it to do absolutely mind-boggling 9-ship formation twinkle rolls the like of which I have never seen since. All those small aeroplanes rotating about their individual x-axes at circa 360 degrees per second while only feet apart had to be seen to be believed. (They always overshot by about 10 deg at the end and had to correct back to wings level. It didn't spoil the effect because they all overshot by the same amount, but they tried very hard to correct it. Eventually someone discovered that the roll acceleration of the Gnat was so high that the eyeballs were rotating axially in the sockets and giving the pilots a false impression of where the horizon was.)
Everyone was happy, not to mention legal, till an ex Red Arrow who had returned to instructional duties flying a Gnat with Fuse 13 in place developed an unusual demonstration for his students. He decided to show them how fast a Gnat could roll by applying full (12deg, fuse in) lateral stick and helping the aircraft round with rudder. He thought this was OK because he did it within the restricted Red Arrows rolling limits. The fin, however, had other views about full rudder at 350 knots and broke in protest. The RAF system then missed the point, over-reacted and insisted that everybody fly with Fuse 13 in place. End of super formation twinkle rolls.
Incidentally, the early development Hawks had a similar restrictor on the aileron angle, in this case being operated by a mechanical plunger on the undercarriage. During development it was discovered that with judicious optimisation of the gearing it was possible to achieve adequate roll rate at high speed, adequate manoeuvrability in the circuit and good handling without the restrictor and it was deleted. MoD asked for some money back in respect of the restrictors which would not have to be manufactured, but I doubt they ever got it.
There was indeed a Fuse 13 on the Gnat. This protected a circuit which restricted the aileron travel to 12 degrees when the U/C was retracted while allowing the full travel of 15 degrees when it was down. This protected the wing and aileron from overstress at high speed while permitting full aileron for manoeuvrability in the circuit. With Fuse 13 fitted and serviceable the aircraft was cleared to rapid roll (full lateral stick, fast as you like) up to about 500 knots and 5g. The Red Arrows realised that they could roll faster with Fuse 13 removed, but far from acting irresponsibly they asked Boscombe if they could rapid roll with it removed if they kept to a more restricted flight envelope. This was investigated with the Design Authority and it was determined that they would be OK if they stuck to 1g rolls at no more than 350 knots. They were happy with this and a proper clearance was issued. The Arrows used it to do absolutely mind-boggling 9-ship formation twinkle rolls the like of which I have never seen since. All those small aeroplanes rotating about their individual x-axes at circa 360 degrees per second while only feet apart had to be seen to be believed. (They always overshot by about 10 deg at the end and had to correct back to wings level. It didn't spoil the effect because they all overshot by the same amount, but they tried very hard to correct it. Eventually someone discovered that the roll acceleration of the Gnat was so high that the eyeballs were rotating axially in the sockets and giving the pilots a false impression of where the horizon was.)
Everyone was happy, not to mention legal, till an ex Red Arrow who had returned to instructional duties flying a Gnat with Fuse 13 in place developed an unusual demonstration for his students. He decided to show them how fast a Gnat could roll by applying full (12deg, fuse in) lateral stick and helping the aircraft round with rudder. He thought this was OK because he did it within the restricted Red Arrows rolling limits. The fin, however, had other views about full rudder at 350 knots and broke in protest. The RAF system then missed the point, over-reacted and insisted that everybody fly with Fuse 13 in place. End of super formation twinkle rolls.
Incidentally, the early development Hawks had a similar restrictor on the aileron angle, in this case being operated by a mechanical plunger on the undercarriage. During development it was discovered that with judicious optimisation of the gearing it was possible to achieve adequate roll rate at high speed, adequate manoeuvrability in the circuit and good handling without the restrictor and it was deleted. MoD asked for some money back in respect of the restrictors which would not have to be manufactured, but I doubt they ever got it.
Sorry, northwing, I was quoting Lee Jones, who led the Team in 1965. He said that Bill Loverseed had first suggested removing Fuse 13, so off they went to try it. Eventually, after getting over the shock of the amazing roll rate which resulted, they were twinkle rolling in close formation
"...and, of course,after a while 'They' caught on to what was happening and so 'They' said "You can't do that, because 'The Girls' at Boscombe Down (the Test Pilots), will have to take a year and a half to check it out" and we couldn't finish the season. So the order was "Replace the fuses immediately". But they didn't say to replace them serviceable, so we got old Bill to blow all the fuses and we put them back blown!"
"...and, of course,after a while 'They' caught on to what was happening and so 'They' said "You can't do that, because 'The Girls' at Boscombe Down (the Test Pilots), will have to take a year and a half to check it out" and we couldn't finish the season. So the order was "Replace the fuses immediately". But they didn't say to replace them serviceable, so we got old Bill to blow all the fuses and we put them back blown!"
Join Date: Jun 2000
Location: Geriatrica, UK
Posts: 1,003
Likes: 0
Received 0 Likes
on
0 Posts
The mechanism was a simple solenoid that restricted stick movement. I'd forgotten about the U/C interlock but there certainly was an IAS switch that I can remember making the stick chatter when flying around the changeover speed.
When Lee Jones led the RAF Aerobatic Team they were painted yellow and called the "Yellow Jacks". They scared the pants off me - particularly at the World Gliding Championships at South Cerney in 1964. They "wired the joint" at 4-6ft in criss-cross and at that height they couldn't have seen all other ac because the airfield has a distinct upside-down saucer shape
When Lee Jones led the RAF Aerobatic Team they were painted yellow and called the "Yellow Jacks". They scared the pants off me - particularly at the World Gliding Championships at South Cerney in 1964. They "wired the joint" at 4-6ft in criss-cross and at that height they couldn't have seen all other ac because the airfield has a distinct upside-down saucer shape
Join Date: Nov 2000
Location: South West
Age: 73
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
fbotcso
You are quite correct.
We used to call the little clicking solenoids the "woodpeckers"!
When turning finals we would fly with them chattering in and out - it saved us having to use our second brain cell to squint at the ASI ! It's a long time ago but as far as I remember they withdrew to give full stick/aileron deflection as the IAS reduced below 155 KIAS or so.
Anyone remember those dreaded STUPRECC drills - whilst trying to control a little jet with the tail stuck at a daft pitch angle. We was men then !
We used to call the little clicking solenoids the "woodpeckers"!
When turning finals we would fly with them chattering in and out - it saved us having to use our second brain cell to squint at the ASI ! It's a long time ago but as far as I remember they withdrew to give full stick/aileron deflection as the IAS reduced below 155 KIAS or so.
Anyone remember those dreaded STUPRECC drills - whilst trying to control a little jet with the tail stuck at a daft pitch angle. We was men then !
Speed below ??400/M0.85??
Trim to the 'Ideal' sector on the Feel Trim gauge
Unlock the elevators ('Click click, white band, 'ELEV' caption on')
Power cock off
Raise the standby trim switch guards
Exhaust the elevator accumulator (11/2 to 21/2 TPI with the gear up, ??51/2 to 6?? with it down)
Check control column response
Check standby trim response and 'TRIM' caption
Changeover (Mod 399 switches) as required
Forgive me if I've got it wrong - I last did that in 1975!
Then there was 'CUBSTUNT' for AC/DC (alternator) failure:
Cabin altimeter cock to 'static'
UHF standby Trx on
Boost pump OFF
Speed below 300/M0.7
Trim to the 'Ideal' sector
Unlock the elevators ('Click click, white band, 'ELEV' caption on')
Non-essential electrics off
Transponder to Emergency
Trim to the 'Ideal' sector on the Feel Trim gauge
Unlock the elevators ('Click click, white band, 'ELEV' caption on')
Power cock off
Raise the standby trim switch guards
Exhaust the elevator accumulator (11/2 to 21/2 TPI with the gear up, ??51/2 to 6?? with it down)
Check control column response
Check standby trim response and 'TRIM' caption
Changeover (Mod 399 switches) as required
Forgive me if I've got it wrong - I last did that in 1975!
Then there was 'CUBSTUNT' for AC/DC (alternator) failure:
Cabin altimeter cock to 'static'
UHF standby Trx on
Boost pump OFF
Speed below 300/M0.7
Trim to the 'Ideal' sector
Unlock the elevators ('Click click, white band, 'ELEV' caption on')
Non-essential electrics off
Transponder to Emergency
Join Date: Nov 2000
Location: South West
Age: 73
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Ah yes...
Then there was "B**G*R" ! when either:
You popped the airbrakes at 450 KIAS and got three greens !
or
You rushed the landing checks on an exotic run and break and heard strange scraping noises on touchdown.
Undercarriage as airbrakes ? great idea.
And what about Cam "K" ?
Then there was "B**G*R" ! when either:
You popped the airbrakes at 450 KIAS and got three greens !
or
You rushed the landing checks on an exotic run and break and heard strange scraping noises on touchdown.
Undercarriage as airbrakes ? great idea.
And what about Cam "K" ?
Join Date: Jun 2000
Location: Geriatrica, UK
Posts: 1,003
Likes: 0
Received 0 Likes
on
0 Posts
1975? Me too.
Cam "K" because it was the one that worked after cams A to J had been rejected.
Weren't we lucky not to have had cam "A"?
Necessary because the fore and aft stick travel was insufficient to cope with the static stability, Mach trim and CG shift in the two-seater (one or two pilots) after the modification from the single seat Midge to the two seat Gnat. It meant that if you trimmed properly the stick was always somewhere in the mid position at most speeds and that you could always get sufficient back stick to "round-out"
, unless you got the unlock wrong!
I bet we've all at some time flopped it onto the runway with the stick right back and hard over one way or the other to cope with the cross-wind.
Always a most demanding and potentially unforgiving advanced trainer.
Cam "K" because it was the one that worked after cams A to J had been rejected.
Weren't we lucky not to have had cam "A"?
Necessary because the fore and aft stick travel was insufficient to cope with the static stability, Mach trim and CG shift in the two-seater (one or two pilots) after the modification from the single seat Midge to the two seat Gnat. It meant that if you trimmed properly the stick was always somewhere in the mid position at most speeds and that you could always get sufficient back stick to "round-out"
, unless you got the unlock wrong!I bet we've all at some time flopped it onto the runway with the stick right back and hard over one way or the other to cope with the cross-wind.
Always a most demanding and potentially unforgiving advanced trainer.
Join Date: Nov 2002
Location: UK, North Riding
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
Gnat roll rate
Northwing.
Unless more than one Gnat lost its fin during a roll, the only one I seem to recall was where the structural failure of the fin was attributed to corrosion of the structure. Valley had a particularly corrosive climate. I certainly remember that thereafter the use of rudder in the air was proscribed except during x-wind landings.
Unless more than one Gnat lost its fin during a roll, the only one I seem to recall was where the structural failure of the fin was attributed to corrosion of the structure. Valley had a particularly corrosive climate. I certainly remember that thereafter the use of rudder in the air was proscribed except during x-wind landings.
That apparatus of student torture the 'Gnat longitudinal control system demonstrator', which taught us all about the Hobson motor, Scissor restrictors, Cam 'K', 'Q' gearing, Datum Shift, '399 Switches' etc was last seen mangled up as a so-called piece of art on the wall of the 'new' groundschool when the JP Mk 6 took over at Valley......and to think of how many folk had been through the agonies of trying to fathom out what all the bits did! It should have been preserved in a museum!
Join Date: Jun 2000
Location: Geriatrica, UK
Posts: 1,003
Likes: 0
Received 0 Likes
on
0 Posts
It could have been an excellent training aid at Cranfield/ETPS to give an analogue demonstration of how a control system can be optimised for a wide range of flight conditions. All done by electronics now which you can't actually "see" working.
(I use the word "optimised" with some reservations!
)
(I use the word "optimised" with some reservations!
)
Thread Starter
Join Date: Jun 2001
Location: England
Posts: 1,006
Likes: 0
Received 0 Likes
on
0 Posts
Alright you've referred to it three times now. What is cam 'K'.
Does anyone know where Folland was based and did they build anything other than the Gnat and the Midge? I presume they eventually became part of the great BAC empire.
Does anyone know where Folland was based and did they build anything other than the Gnat and the Midge? I presume they eventually became part of the great BAC empire.
FOLLAND AIRCRAFT Co.Formed at Hamble in 1936 as British Marine Aircraft Ltd.(associated with British Aircraft Manufacturing Co.Ltd).The intention was to manufacture the Sikorsky S42 flying boat,but this project was abandoned.In 1937 H.P.Folland became Managing Director and the company was renamed Folland Aircraft Co.The company then concentrated its efforts on subcontract / component work until 1940.
During 1940 the company built 12 "large engine test" aircraft for the flight testing of large piston engines.The next production did not happen until 1954 when the Midge (prototype for the Folland Gnat ) first flew(At Chilbolton).This was followed by production of some 120 aircraft for the RAF ,India,Yugoslavia and Finland.As with the Midge ,all were transported to Chilbolton for flight testing.During this time the company became part of Hawker Siddelly Aviation,which ,in turn later became part of British Aerospace.No further complete aircraft were built at Hamble.Instead,major components were manufactured,principally for Harriers.
From the Hampshire Aviation History website:
http://daveg4otu.tripod.com/aviation...2000/id21.html
During 1940 the company built 12 "large engine test" aircraft for the flight testing of large piston engines.The next production did not happen until 1954 when the Midge (prototype for the Folland Gnat ) first flew(At Chilbolton).This was followed by production of some 120 aircraft for the RAF ,India,Yugoslavia and Finland.As with the Midge ,all were transported to Chilbolton for flight testing.During this time the company became part of Hawker Siddelly Aviation,which ,in turn later became part of British Aerospace.No further complete aircraft were built at Hamble.Instead,major components were manufactured,principally for Harriers.
From the Hampshire Aviation History website:
http://daveg4otu.tripod.com/aviation...2000/id21.html
Join Date: Jun 2000
Location: Geriatrica, UK
Posts: 1,003
Likes: 0
Received 0 Likes
on
0 Posts
18 Greens, to tell you about Cam "K" would be to destroy your innocence. An explanation will rival the spiral staircase in an explanation without the use of hand gestures.
The ratio of stick movement to tailplane movement was non-linear and also varied with the height and airspeed. With such a short stick travel because of the cramped cockpit, and to ensure that sufficient tailplane movement was available at low speed whilst not leading over controlling at high speed, Q-gearing (that's "Q" as in ˝rho x v˛) and Cam "K" were developed. Cam "K" was the final success after a succession of Cams were tried.
The Gnat also had Folland's own version of an Ejection Seat, known as the "Folland Humane Killer" simply because the safety/disarming mechanism was a handle that pressed on the back of the pilot's head when safe and that the groundcrew could reach to rotate sideways to arm the seat.
The raising/lowering mechanism of the seat pan had a habit of not locking the seat pan although it felt as though it had. Some pilots who ejected had severe thigh injuries when the seat frame went up the rails while they stayed still in the unlocked seat pan until the pan reached the bottom of the range of adjustment, started to move abruptly and hit them hard under the thighs.
An explanation will rival the spiral staircase in an explanation without the use of hand gestures.The ratio of stick movement to tailplane movement was non-linear and also varied with the height and airspeed. With such a short stick travel because of the cramped cockpit, and to ensure that sufficient tailplane movement was available at low speed whilst not leading over controlling at high speed, Q-gearing (that's "Q" as in ˝rho x v˛) and Cam "K" were developed. Cam "K" was the final success after a succession of Cams were tried.
The Gnat also had Folland's own version of an Ejection Seat, known as the "Folland Humane Killer" simply because the safety/disarming mechanism was a handle that pressed on the back of the pilot's head when safe and that the groundcrew could reach to rotate sideways to arm the seat.
The raising/lowering mechanism of the seat pan had a habit of not locking the seat pan although it felt as though it had. Some pilots who ejected had severe thigh injuries when the seat frame went up the rails while they stayed still in the unlocked seat pan until the pan reached the bottom of the range of adjustment, started to move abruptly and hit them hard under the thighs.
Thread Starter
Join Date: Jun 2001
Location: England
Posts: 1,006
Likes: 0
Received 0 Likes
on
0 Posts
Wub,
I suppose thats why there is a Gnat gate guardian outside the old Hamble Airfield. Silly me.
Fob,
Consider my innocence destroyed. Thanks for the explanation.
As I learn more of the complexities and systems in this aircraft the less keen I am to fly it. If any of these systems failed was there a manual reversion not including the ejection seat?
18
I suppose thats why there is a Gnat gate guardian outside the old Hamble Airfield. Silly me.
Fob,
Consider my innocence destroyed. Thanks for the explanation.
As I learn more of the complexities and systems in this aircraft the less keen I am to fly it. If any of these systems failed was there a manual reversion not including the ejection seat?
18
Cam 'K' was very simple - the input was from the control column and the output non-linear. Nothing more than a cleverly shaped pulley and rod system. So small deflexions gave control precision around neutral as the more circular bit of the cam moved, but larger ones gave a much greater output as the more pointy bit moved. The output value was then modified depending on speed - a simple plunger moved in respect to ram air pressure and moved a fucrum in the pitch system to modify the pitch control output accordingly. The output then entered the infamous 'Hobson motor'- an hydraulic motor which moved the slab tail. (Groundschool question 'List the 18 components of the Hobson motor'.......). This device also had a 'scissor restrictor' to stop you moving the control column too fast for Mr Hobson's device to cope with! Because there was no 'natural' control feel in pitch, a 'feel trim' system of a force v. displacement spring tube would take care of that - operated (normally) by electrical stick-top switches, although the position of 'neutral' in pitch moved as IAS increased... Another Gnat system was 'datum shift'; because the Cof G moved forwards as the landing gear extended, a bit of bike chain was wrapped around the gear actuator and as it moved, it added an extra 3(?) deg of pitch input to compensate.....
If the hydraulics failed, you had to act very quickly. First do whatever you needed to do to get the speed below 400KIAS or M0.85. Then move the feel trim so that it was in the 'ideal' sector on the feel trim position indicator, then 'unlock' the little elevators on the trailing edge of the slab tail to assist with pitch control; to make sure that you'd pulled the lever far enough, you counted 2 clicks, checked that a white tell-tale band was visible and that the 'ELEV' caption illuminated. Turn off the hydraulic power supply cock to the tailplane.....now the fun bit. Raise the standby trim switch guards so that you could operate Mr Hobson's device....electrically! But it would only move up from the position at which the hydraulics failed - so you had to exhaust the residual pitch accumulator pressure with the Hobson motor at (I think) 2 1/2 to 3 deg up on the tailplane position indicator or 5 1/2 to 6 with the landing gear down (datum shift didn't work with a hydraulic failure). Then you exhausted the aileron accumulator pressure until a hardening up in roll was noted. Now check that the tailplane will move electrically by moving the standby trim switches - and checking that the 'TRIM' caption illuminated, then check that you had control in roll. The control column only moved the little elevators in this mode, so primary pitch was effected by moving the standby trim switches; pitch trim was effected by....moving the control column - the complete converse to the normal method! The idea was to operate the system to keep the control column 'load-free and central'; to make it even more fun, you could transfer the standby trim switch function to the now-redundant stick-top feel trim switches by opertaing a further pair of switches known as the '399s' as they were fitted post-mod 399.
As you approached for landing - at around 150 kts - you had to preset the slab tail to (I think)51/2 to 6 deg up on the TPI gauge and push the control column to hold the correct attitude; you then relaxed the push and changed to a back pressure to flare.
Fun, eh? But we used to do night manual rollers in the little $od - at Mona!
Don't be put off; it's a wonderful little jet but fiendishly complicated and it MUST be maintained correctly and flown by someone who can cope with its foibles instinctively! It's nearly 30 years since I had my last trip in a Gnat and I'd love to have another chance if I ever had the opportunity!!
If the hydraulics failed, you had to act very quickly. First do whatever you needed to do to get the speed below 400KIAS or M0.85. Then move the feel trim so that it was in the 'ideal' sector on the feel trim position indicator, then 'unlock' the little elevators on the trailing edge of the slab tail to assist with pitch control; to make sure that you'd pulled the lever far enough, you counted 2 clicks, checked that a white tell-tale band was visible and that the 'ELEV' caption illuminated. Turn off the hydraulic power supply cock to the tailplane.....now the fun bit. Raise the standby trim switch guards so that you could operate Mr Hobson's device....electrically! But it would only move up from the position at which the hydraulics failed - so you had to exhaust the residual pitch accumulator pressure with the Hobson motor at (I think) 2 1/2 to 3 deg up on the tailplane position indicator or 5 1/2 to 6 with the landing gear down (datum shift didn't work with a hydraulic failure). Then you exhausted the aileron accumulator pressure until a hardening up in roll was noted. Now check that the tailplane will move electrically by moving the standby trim switches - and checking that the 'TRIM' caption illuminated, then check that you had control in roll. The control column only moved the little elevators in this mode, so primary pitch was effected by moving the standby trim switches; pitch trim was effected by....moving the control column - the complete converse to the normal method! The idea was to operate the system to keep the control column 'load-free and central'; to make it even more fun, you could transfer the standby trim switch function to the now-redundant stick-top feel trim switches by opertaing a further pair of switches known as the '399s' as they were fitted post-mod 399.
As you approached for landing - at around 150 kts - you had to preset the slab tail to (I think)51/2 to 6 deg up on the TPI gauge and push the control column to hold the correct attitude; you then relaxed the push and changed to a back pressure to flare.
Fun, eh? But we used to do night manual rollers in the little $od - at Mona!
Don't be put off; it's a wonderful little jet but fiendishly complicated and it MUST be maintained correctly and flown by someone who can cope with its foibles instinctively! It's nearly 30 years since I had my last trip in a Gnat and I'd love to have another chance if I ever had the opportunity!!
