AIRWORTHINESS APPROVAL NOTE NO: 26120
APPLICANT: P A Greenhalgh & B Green, Fast Jets Ltd
AIRCRAFT TYPE: Aero Vodochody, L-29 Delfin
REGISTRATION NO: G-DELF
CONSTRUCTOR'S NO: 194555
OPERATOR: Fast Jets Ltd
CERTIFICATE CATEGORY: Permit-to-Fly
To approve Aero L-29 Delfin registered G-DELF
for the issue of a Permit-to-Fly.
1. Introduction
The L-29 Delfin is a two seat jet trainer which was designed and manufactured by Aero Vodochody, at Kunovice,
Czechoslovakia. The turbojet engine designated the M701c - 500 was also designed and manufactured in
Czechoslovakia by Walter at its Motorlet works.
The first studies leading to the Aero L-29 was made in 1955 by a team under K. Thomas and Z. Rublic. Known as
the XL-29, the prototype flew for the first time on 5 April 1959, powered by a Bristol Siddeley Viper turbojet. The
second prototype, which made its initial flight in July 1960 and a small pre-production batch of L-29s for service
evaluation, had the M 701 turbojet. A year later the Delfin was subjected to competitive evaluation against the
Yakovlev Yak-30 and PZL-Mielec TS-11 Iskra. As a result, all Warsaw Pact countries (except Poland, which
decided to continue supporting its own TS-11) decided to adopt the Delfin as their standard basic and advanced jet
trainer. The first production Delfin was completed in April 1963, and approximately 3,600 had been built before
the run ended some 12 years later to be replaced by the L-39 Albatros.
2. Description
The L-29 Delfin is a tandem two-seat basic and advanced jet trainer with tapered wings and a horizontal stabiliser
mounted on top of the vertical stabiliser. The design concept of the L-29 is based upon a straight-forward, easy-to-
build structure which is simple to fly and uncomplicated to operate. Runway requirements are modest, and it can
operate from grass, sand or water-logged airstrips.
Flight controls are manual, with generous wing flaps and a solid airbrake on each side of the rear fuselage. The
Delfin does not readily stall or spin, and its safety and reliability are said to be high. There is an emergency
manual backup for carriage extension and the lowering of landing flap.
Both cockpits are pressurised and are provided with ejection seats with canopy jettison being performed by
pneumatically operated piston actuators.
A detailed description of the aircraft may be obtained by reference to the publications listed in section 6.
3. Approval Basis
The aircraft was designed to Russian military requirements broadly equivalent to Def Stan 00-970 although not
directly comparable. CAA approval is based on the satisfactory service history of the type and investigation
carried out in accordance with policies agreed by ARB during the meeting of 23 rd April 1992 appropriate to its
classification in the intermediate category. The aircraft's safety record is acceptable to CAA.
4. Technical Investigation
The applicants have submitted information on type safety record based on extracts from official DOSAAF
documents in accordance with BCAR A3-7 Appendix 1 para 2.1 and this record is acceptable to the CAA 1. The
applicants engaged J S Chillingworth to establish conformity to type (BCAR A3-7 Appendix 1 para 2.2.) and
support submission of this aircraft to the CAA for Permit issue. The aircraft was surveyed for potentially
hazardous features in accordance with BCAR Section B3-7 para 3(d) and the results are described below.
Unusual features of the aircraft include simulated failure modes selectable from the rear seat. These features were
intended as training aids but these facilities are not accepted for Permit issue as the pilot-in-command must be sure
of retaining full authority throughout flight. These modes have been disabled under the applicant’s modification
actions described in Section 4.1 (b).
L-29 Delfin, serial number 194555 was delivered to the Soviet Air Force in October 1971 where it remained in
service until May 1991 when it was placed in long term storage and preserved. This aircraft was purchased in
1995 together with four other Delfins by Mr Ravio Susi an Estonian aircraft dealer.
These aircraft were dismantled and shipped to Tartu Airport in Estonia where they were re-assembled by Russian
technicians under the supervision of Mr S Gorokh who is the Chief Engineer at Zaporozhye, a Ukrainian airbase
which still operates 105 L-29 Delfins. After re-assembly, a full military flight-test profile was conducted by Mr V
Gorak who is the Flying Standards Officer at Zaporozhye. A submission was made to the Estonian CAA and
194555 and the other aircraft were granted civilian Airworthiness Certificates in the Normal/Aerobatic category in
December 1995.
In July 1996 the aircraft was ferried to the UK from Tartu by Mr Gorak and the aircraft subsequently operated until
October 1996 from RAF Manston.
At the time of this permit application, the airframe and engine hours are shown in table 1.
Service Use Civilian Use Total
Airframe 2678.30 36.50 2715.20
Engine 1310.40 38.55 1349.35
Table 1: Aircraft Utilisation
4.1. Modification State
The applicants have ascertained that no alterations have been made, damage incurred or significant repairs
to the main structure of the aeroplane. Unlike Western aircraft which have ongoing modification
programmes. Aero Vodochody ‘freeze’ the modifications at build standard. It has been determined that any
modifications issued after the time of build in 1971 and the last airframe overhaul in 1984 have been
implemented. Some minor modifications were made to the aircraft during the period of Estonian
registration and subsequently some other modifications were made by the applicants
______________________________
1
Flight Safety Analysis: L-29 Delfin
4.1(a) Estonian Modifications2
The modifications made during the period of Estonian registration were not of a structural nature. No
formal record of these modifications is available but a survey of these modifications indicates that these
were carried out to a satisfactory standard. The modification were:
(i) Exchange of front & rear metre reading altimeters for units calibrated in feet.
(ii) Installation of King KN76A transponder and altitude encoder.
(iii) Removal of front cockpit tank jettison switch.
(iv) Removal of gun sight and camera from front cockpit.
(v) Removal of military 020 IFF transponder.
4.1(b) Applicants Modifitions3
Applicants modifications have been carried out, as follows:
(i) Inhibition of simulated failure modes from rear seat
Simulated Failure How Inhibited
Pitot & static pressure: failure by 2 switches Lock switches with 20 swg
wire to Normal position
Attitude indicator: failure by 2 switches Lock switches with 20 swg
wire to Normal position
Undercarriage lowering: failure by switch Lock switches with 20 swg
wire to Normal position
Landing light over-ride switch Lock switches with 20 swg
wire to Off position
Isolation valve switch Lock switches with 20 swg
wire to Normal position
Instrument, intercom and Master switches on main panel Lock switches with 20 swg
wire to On position
Drop tank jettison switch Lock switches with 20 swg
wire to Safe position and cov
guard
(ii) Removal of redundant military equipment
Equipment
APK9 ADF receiver & twin turner units
ADF inverter & transformer
ADF Gonio
Flight data recorder
(iii) Oxygen system
Oxygen system was disabled and the 3 four litre Oxygen bottles used to enhance the capacity of the
Nitrogen based braking system.
(i) Braking system
The capacity of the braking reservoir was increased from 8 litres to 20 litres by connecting
unused Oxygen bottles to the Nitrogen system.
________________________________
2
TG Modification Reference TGM/Mod1/98
3
TG Modification Reference TGM/Mod2/98
4.2.
4.3. Structure - Fatigue State
A manufacturer’s communication states that the airframe life is nominally 5000 hours provided that all airframe
overhauls have been carried out. 4 All such overhauls have been performed by factory agreed agencies for
194555 with the last one at 2010:10 hours in March 1984. An extension beyond 5000 hours is permissible
on an on-condition basis. The maximum interval between overhauls is 1200 hours. This information is
derived from the logbook front page for this aircraft, which is series 9.
The remaining airframe fatigue life at permit application is therefore:
5000 - 2715: 20 = 2284 hours: 40 minutes
Remaining airframe time before overhaul is therefore:
1200 - 705:10 = 494 hours: 50 minutes
Load factors are up to +7/-3.5g with external tanks fitted. An aural tone is heard when these limits are approached,
A single g-meter is fitted to the front cockpit but is clearly visible from the rear.
4.3. Engine
The aircraft is powered by a Walter Motorlet M70c-500 turbojet engine. It has a single-sided centrifugal
compressor and a single stage axial flow turbine. Compressor bleed air is taken from the engine to provide
cabin pressurisation, de-icing, air-conditioning and pressurisation of the external fuel tanks. Engine driven
accessories are the HP fuel pump, hydraulic pump, generator and a tacho-generator for the dual RPM
indicators.
The engine fitted to 194555 serial number c63131 which prior to flight test had completed a total of 1349 hours: 45
minutes and 161 hours: 45 minutes since overhaul. Time between overhauls is stated as 500 hours and a
service life of 4000 hours (to be confirmed by applicant).5
The remaining life left to run on the engine at permit application is therefore:
500 - 161:45 =338 hours: 15 minutes.
The limitations stated in the engine Technical Manual 6 are consistent with those contained in the Flight Manual 7 and
are quoted in Section 8, Limitations.
Fire warning and extinguisher systems are provided and operational. The HP fuel control system consists of a fully
automatic governor which provides the correct fuel flow for any demanded throttle position. The fuel
control system ensures controlled acceleration during the start cycle, limits the maximum RPM achievable
under all conditions and provides barometric compensation. To accommodate a failure in the HP fuel
system there is a pilot activated valve duplicated in both cockpits which bypass the fuel around the fuel
metering devices. The activation of this valve is indicated in the cockpit by a warning on the Caution and
Warning Panels.
The engine is equipped with an electrically driven starter, located in the air intake nose cone. A clutch connects the
starter with the engine and automatically disconnects when the rotor RPM is higher than the starter
revolutions. A starting control box applies the appropriate signals to the ignition unit and the starter motor
to provide fully automatic control over the start sequence. The duration of this automatic cycle is 17
seconds with the engine becoming fully self sustaining 30 seconds later.
A separate air starter button is also provided which supplies continuous ignition for 19 seconds but no starter
engagement.
_________________________________
4
Manufacturers Communications
5
Engine Logbook II page 167
6
TG110 M701c-500 Service instructions
7
TG 100 L-29 Delfin Flight Manual
___________________________
4.4. Controls
All primary flight controls are mechanically operated through control rods. The angle of attack of the tailplane
moves electrically in response to the flap setting selected. This feature is intended to minimise pitch
changes as flap is lowered and raised. Guidance from the Flight Manual suggests that if failure of the
actuator motor leaves the tailplane in the incorrect position, then the aircraft can be safely flown with
manual trim and acceptable stick forces.
4.1. Systems General
In general all systems in the aircraft are operational with the exception of the oxygen system which has been
disabled to provide a greater reservoir capacity for the brakes. As a consequence of this the owner has
elected not to operate the aircraft above 10,000 feet, and this is now listed as a limitation. The cabin
pressurisation has not been disabled however as it is combined with the cabin air-conditioning and heating
system which is to be retained.
Undercarriage
The undercarriage is hydraulically extended and retracted and has a extension and operating speed limit of 290 kph.
An hydraulic accumulator provides emergency pressure for undercarriage extension in the event of a pump
failure.
Brakes
The braking system is actuated by a ground replenishable source of Nitrogen or air at a pressure of 150 Bar. The
brakes are differently controlled by rudder bar deflection and applied by a lever mounted on the control
column. When the undercarriage is raised the brakes are automatically applied briefly.
Flaps
The flaps are hydraulically operated with an extension and operation speed limit of 270 kph. The flaps will retract
automatically if this speed is exceeded. An hydraulic accumulator provides emergency pressure for flap
and undercarriage extension in the event of a pump failure.
Air brakes
The air brakes are hydraulically extended and automatically open when the speed exceeds MACH 0.7.
Pitot/static
Duel selectable systems are provided.
Fire Warning
Multi-sensor fire detectors are placed in the rear fuselage and are activated by excessive rate-of-change of
temperature.
Fire Protection
A pyrotechnically discharged fire bottle can be activated from the cockpit directly into the engine bay in case on of a
fire.
4.2. Ejection Seats
Ejection seats based on pyrotechnic cartridges are fitted in both front and rear cockpits. The seats can be operated
above heights of 1500’ AGL and speeds below 800 km/h. The canopies are jettisoned by pneumatically
powered pistons raising the leading edges of the canopies in to the airstream. Canopy separation removes a
blocking pin allowing the seat firing handle to be squeezed. Simultaneous ejection is prevented by an
electro-pnematic blocking circuit which prevents the second occupant ejecting until the first has left the
aircraft. This sequencing may be disabled in special circumstances by pulling a de-blocking D-ring.
Vital seat checks will be performed at annual inspections of the seats and after each installation. Duplicate
inspections of the seat locking to the airframe will also be performed after each installation.
4.3. Fuel System and Drop Tanks
The fuel tank consist of two main fuselage tanks mounted between the rear cockpit and the engine. They are
interconnected by two balancing hoses. Fuel to the engine is drawn from the rear tank through an inverted
flight reservoir which provides fuel for 15 seconds of inverted flight. An electrically driven LP fuel pump
is mounted at the base of the rear fuselage tank and the whole fuel system may be isolated at the tank base
by activating the LP fire-cock. This is closed by compressed Nitrogen and is controlled by operating the
fire cock handle from either cockpit.
Total usable capacity of the two fuselage tanks which are filled through a single filler cap is 1000 litres. Two
additional external tanks are mounted on pylons under the wings. These tanks hold 150 litres each and the
fuel is transferred to the main tanks by compressed air obtained from the engine. Fuel transfer is controlled
by a float valve in the main tanks. Although aircraft 194555 has a total usable capacity of 1300 litres.
A low-fuel light activated when 200 litres remains is included on both front and rear caution and warning panels.
The switch that jettisons the drop tanks has been removed from the front cockpit and a similar switch in the rear
cockpit has been wire-locked into the safe position.
4.4. Weight and Balance
The aircraft is accepted by the CAA at 3550 kg MTWA. Maximum landing weight is 3285 kg. A weight and
balance schedule reference 98MAR111 dated 6 th March 1998 has been prepared by Steve Cook Aircraft
Loading and Trim Services and appended to the Flight Manual. The acceptable centre of gravity range has
been determined by the manufacturer to be between 20.5% and 25.5% of the Mean Aerodynamic Chord
(MAC) which is 2.04m and the datum is at Fuselage Frame 11. These figures have been re-established in
report 98MA111 and schedule 98MA111 using units of mm relative to a new datum declared at 4300 mm
forward of Frame 11.
The weight schedule referenced above calls for 19 kg ballast at 1163 mm. The applicant has, however, opted to use
15 kg ballast at 163 mm which yields the same forward and aft CG positions. This has been recorded in
the Flight Manual Supplement.
4.5. Electrical system
A battery master switch is provided and a generator warning in both cockpits indicates when operating on internal
battery power alone. The battery endurance in an emergency meets the requirements of Airworthiness
Notice 88. Load shedding procedures will be added to the Flight Manual
The 28VDC system is provided by a single lead-acid charged by an engine driven 3 kW generator. A volt-ammeter
is provided in both cockpits. AC power for flight and remaining radio systems is provided by two, 36V
400 Hz inverters and one 115v 400 Hz inverter.
4.6. Avionic System
The original military equipment has been rendered inoperative or removed with the exception of the Baklaw5 VHF
communications transceiver. The only avionics fitted and operable are as follows:
Qty Type Function Approval
1 Baklan 5 760 Channel VHF Comms Tranceiver LA301034
1 King KT76A Transponder LA208
4.11. Operational Aspects
The operators Operational Control Manual has been submitted to the CAA Sports and Recreational
Department for approval to CAP 632. Approval by CAA letter T10Z/13/018/G-DELF was granted.
Maximum duration for inverted and negative g flight is 15 seconds following which a period of 30 seconds
of positive g flight must be flown to allow the inverted fuel reservoir to refill.
The aircraft may take-off and land on grass surfaces.
5. Flight Test
The aircraft was flight tested by the applicant on 8 & 10 April 1998 to L29 FLIGHT TEST CERTIFICATE and
concludes that the aircraft is acceptable for the issue of a Permit to Fly.
A CAA handling assessment has been carried out and reported in FTR/10421P. The performance and handling was
acceptable to CAA.
6. Manuals
The applicants have a complete set of technical manuals which were produced in English by Aero Vodochody. The
flight manual is essentially that prepared by Dornier for the Nigerian Air Force. The following manuals are
available; the documents marked * have been authored by personnel of Fast Jets Ltd or TG Aviation Ltd.
Book Title
Reference
TG100 L-29 Delfin Flight Manual (includes Pilot’s Check List)
TG100/G-DELF L-29 Delfin Flight Manual Supplement for G-DELF
TG101 General Data of the L-29 Aircraft
TG102 Technical Description of the Airframe
TG103 Technical Description of the Electrical, Instrument Oxygen & Radio Systems
TG104 Technical Description and Instruction for Operation of Aircraft Armament
TG105 Servicing and Maintenance of Canopy Jettison and Ejector seats*
TG106 Periodic Inspection of the L-29 Aircraft
TG107 TG Aviation Maintenance Schedule for L-29 Aircraft*
TG108 Airframe Parts Manual Volume 1
TG109 Airframe Parts Manual Volume 2
TG110 M701c -500 Service Instructions
TG111 M701c -500 Parts Manual
TG112 TG Aviation Maintenance Schedule for M701c -500 Engine*
7. Noise Certificate
A noise certificate is not required for this aircraft as it operates on a Permit to Fly.
8. Limitations and Concessions
Airframe and engine limitations are given in the Flight Manual TG100. Key limitations and concessions are
shown below. Items marked * are to be placarded or marked on instruments
Reference Limitations /concession
1 Aerbatics are permitted in accordance with the Flight Manual. Flick manoeuvres, intentional
stalling and spinning are prohibited.*
2 Load factor +7.5\3.5g. Negative g limited to 15 seconds.*
3 C of G to be between 20.5% and 25.5% of MAC. MAC is 2.04m and datum is at Fuselage
Frame 11.
4 Max take-off weight -: 3550 kg, Max landing weight -: 3285 kg
5 Airspeed Limitations:
Max Speed* 820 km/h
Mmax* 0.7 Mach
Undercarriage lower/raise* 290 km/h
Flaps 15 or 30 lower 270 km/h
Maximum crosswinds 43 km/h (23kts)
6 Engine limitations
Conditions RPM(%) JPT (C) Duration
Maximum Speed* 100 700 6 minutes
Normal rated speed* 97 700 30 minutes
Maximum continuous* 94 700 No limit
Idle* 35 550 No limit
Oil pressure minimum 0.5kg/cm2 at idle 35%.*
Oil pressure maximum 2.5kg/cm2 at full power 100%.*
Oil pressure minimum 20C*
Oil pressure maximum 110C.*
7 Day VMC only*
8 No Smoking*
9 Maximum altitude 10,000 ft
9. Maintenance
The manufacturers servicing schedule for the L-29 is defined in book reference TG106 and TG107. Inspections
are called for at 50, 100 and 200 hours and multiples thereof up to the 1200 hour overhaul. These times have
allowable margins of - 10% /+20%. Due to the expected low utilisation under the Permit to Fly, the applicant has
proposed the following calendar maintenance check cycle:
Permit to Fly issue 200 hr inspection
First year Permit renewal 100 hr inspection
Second year Permit renewal 200 hr inspection
Third year Permit renewal 100 hr inspection
Fourth year Permit renewal 200 hr inspection
and so on
This maintenance check cycle is acceptable to the CAA provided the flying hours called up in the manufacturers
servicing cycle are not exceeded.
This aircraft must be maintained by a company approved under BCAR A8-20 with a rating for the aircraft type and
experience in the maintenance of the ejection seats. The aircraft is to be kept hangared and inhibiting/short term
care and maintenance procedures observed.
This aircraft has been inspected and found to conform to the requirements of the AAN and to be in a satisfactory
and airworthy condition.
10. Approval
This aircraft G-DELF Constructors Number 194555 is approved for issue of a Permit to Fly provided that it is
operated accordance with the limitations and procedures in documentation in documentation referred to in Section
6 above, and in Section 8 above, and the conditions of the Permit to Fly and that it is maintained in accordance
with all appropriate manuals and schedule including publications referred in Section 6.
R J Hardy
..........................................................
For the Civil Aviation Authority
Date 28 April 1998
