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Bundesstelle fürFlugunfalluntersuchung German Federal Bureau of Aircraft Accident Investigation

Investigation Report The investigation was completed stating facts only, i.e. no analysis and conclusions.

Identification

Type of Occurrence: Serious Incident

Date: 28 December 2018

Location: Near Faro, Portugal

Aircraft: Airplane

Manufacturer: Learjet

Type: Model 31A

Injuries to Persons: No injuries

Damage: Aircraft was not damaged

Other Damage: None

State File Number: BFU18-1808-6X

Abstract

During descent, at 11,500 ft Pressure Altitude (FL 115), the flight crew conducted a

flight manoeuvre (roll) not intended for transport aviation.

Investigation Report BFU18-1808-6X

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Factual Information

History of the Flight

On the day of the occurrence, take-off took place at 1022 hrs1 at London Biggin Hill

Airport, United Kingdom. Airport of destination was Faro, Portugal. It was a

positioning flight without passengers conducted under instrument flight rules. The

Pilot in Command (PIC) occupied the left-hand seat and was pilot flying. The co-pilot

occupied the right-hand seat and was pilot monitoring. Two employees of the

company were seated in the cabin.

The following description of events is a based on analysed Flight Data Recorder

(FDR) data and witnesses’ statements.

After about one hour of flight time, at 1130 hrs, the aircraft was in Portuguese

airspace. During descent, the PIC asked the co-pilot if he agreed to fly a roll about

the longitudinal axis of the aircraft.

The co-pilot provided the BFU with a written statement that he did not agree to such

a flight manoeuvre and had told the PIC so. According to the co-pilot’s statement and

the FDR data, the PIC had disengaged the autopilot at 1136:50 hrs at about

13,200 ft2 Pressure Altitude (PA) and flown the airplane manually.

At 1137:10 hrs, at about 11,500 ft PA, two steep turns with a bank angle3 of about

140° each were flown left and right. At 1138:15 hrs, the PIC conducted the roll about

the longitudinal axis of the airplane, also at about 11,500 ft PA levelling-off occurred

10 s later.

The flight manoeuvre was initiated with 301 kt IAS4. During the roll, airspeed

decreased continuously. Levelling-off occurred with 251 kt IAS. During the initiation

of the flight manoeuvre a maximum load factor of +2.47 g occurred, which decreased

continuously to +1.00 g (Fig. 4).

During the flight no one was injured. At 1149 hrs, landing occurred at Faro Airport,

Portugal.

1All times local, unless otherwise stated. 2 Based on FDR data the PA was measured at 1,013 hPa. 3 FDR Parameter 4 FDR Parameter


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Occurrence Report

In May 2019, the operator charged another company with the routine read-out of the

FDR data as part of the Flight Data Monitoring (FDM5). After the read-out, the flight

manoeuvre was identified due to the exceptionally high roll angle data. On

4 June 2019, the operator reported the occurrence with the BFU.

Personnel Information

Pilot in Command

The 44-year-old PIC held an ATPL(A) initially issued on 20 March 2014 by the

Luftfahrt-Bundesamt in accordance with Part-FCL.

The licence listed the following ratings:

Aircraft type Licence entry: Valid: Learjet 20/30 PIC IR 31 December 2018

Learjet 45/75 PIC IR 30 November 2019

Piper PA31T/42 PIC IR 31 May 2019

Piper PA31T/42 TRI 30 April 2019

Ratings: Licence entry: Valid: SEP (Land) PIC 31 March 2020

SEP (Land) IR 28 February 2019

FI (A) CPL, PPL, SE SP, Night,

Aerobatic (A), Instructor,

Instrument Rating

30 April 2019

Aerobatic No expiry date

The BFU was provided with a class 1 medical certificate valid until 16 March 2020.

The PIC had a total flying experience on Learjet 31A of 439 hours.

For the PIC this was the first flight of the day.

5 ICAO Annex 6 Art. 3.6.3 mandates since 1 January 2005 that airlines operating aircraft with a maximum take-off

mass of more than 27,000 kg conduct FDM. For aircraft with a maximum take-off mass of more than 20,000 kg, ICAO Annex 6 Art. 3.6.2 recommends the performance of FDM since 1 January 2002, but voluntarily.


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Co-pilot

The 33-year-old co-pilot held an ATPL(A) initially issued on 12 December 2013 by

Luftfahrt-Bundesamt in accordance with Part-FCL.

The licence listed the following ratings:

Aircraft type Licence entry: Valid: Learjet 20/30 PIC IR 31 December 2019

The BFU was provided with a class 1 medical certificate, valid until 8 June 2019. The

co-pilot had a total flying experience on Learjet 31A of 1,607 hours.

For the co-pilot this was the first flight of the day.

Other Personnel

Two other persons were on board, but had no flying functions.

Aircraft Information

The Learjet 31A of Learjet Incorporation is a twin-engine low-wing aircraft in all-metal

construction. It has a two-person cockpit and a cabin for up to nine passengers.

Originally, it was designed as short and medium range business jet.

The aircraft had a German certificate of registration and was operated by a German

operator in commercial passenger transport.

General Aircraft Data

Manufacturer Learjet Incorporation

Type 31A

Manufacturer’s Serial Number 155

Operating Time 7,570 hours

Landings 6,146

Engines Honeywell Aerospace, TFE731-2

Wing Span 13.36 m


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Length 14.36 m

Maximum take-off mass 7,711 kg

Maximum landing mass 7,257 kg

The aircraft was equipped and operated for ambulance flights.

The three-way view in Figure 2 shows the dimensions of the aircraft type and the

location of the door on the left side of the aircraft.

The image is an excerpt from the Operation Manual, Part B-LJ31A, Chapter

Limitations, 15.12.2016.

Fig. 1: Ambulance configuration (viewed from above) Source: Operation Manual, Part B-LJ31


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Documentation

The Journey & Technical Log of the airplane did not show any entry in the Minimum

Equipment List (MEL).

Fig. 2: Three-way view Learjet 31A Source: Operation Manual, Part B-LJ31A


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Aerobatics

The operator’s Operation Manual Part-B-LJ31A, Chapter Limitations, 15.12.2016,

prohibited aerobatics. The following is an excerpt:

[…]

Manoeuvres

- no aerobatic manoeuvres, including spins, are approved.

- intentional stalls are prohibited above 18,000 feet with flaps and/or landing

gear extended

[…]

Inertial Navigational System

The manufacturer stated in the data sheet for the inertial navigational system KAU-

461 of 10.12.1987 the following:

Chapter 2.2 System Overall Performance

The System performs as specified within the following limits:

Angular rates in any body axis max 150 deg / sec

Accelerations in any body axis max +- 8 g

Output values are limited to +- 4 g and 128 deg / sec as required in

ARINC 705.

Manoeuvring Speed

Manoeuvring Speed (VA) is a speed limitation by the aircraft manufacturer. At air

speeds (IAS) above the maximum VA full deflection of the control surfaces may

cause aircraft structure damage.

The operator’s Operation Manual Part-B-LJ31A, Chapter Limitations, 15.12.2016,

showed a graph (Fig. 3) of the VA in relation to altitude, mass and speed. The load

factor for flight manoeuvres with retracted flaps was +3.0 g6 to -1.0 g. Based on the

graph, maximum allowable VA can be determined in relation to altitude and aircraft

mass.

6 The load factor is defined as force per unit mass, i.e. acceleration.


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Figure 3 is an excerpt of the Operation Manual. The BFU drew in the FDR data of the

flight manoeuvre in red. The initiation of, the inverted part of the flight manoeuvre and

levelling off were above the allowable manoeuvring speed.

Meteorological Information

At the time of the incident it was daylight. The Deutscher Wetterdienst (German

meteorological service provider, DWD) provided the BFU with wind charts of different

altitudes and ICAO Area C SIGWX7 charts. The charts show that at the time of the 7 Significant Weather of Europe and Africa. The World Area Forecast Centre (WAFC), London, compiled the data.

Fig. 3: Manoeuvring speed for Learjet 31A Source: Operation Manual/adaptation BFU


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occurrence, no turbulence or thunderstorm cells were present along the flight route.

At FL120, an eastern wind current with a speed of about 10 kt prevailed. According to

the weather radar image8 of 1000 hrs, a thin cloud layer was located at the area of

the occurrence.

Aids to Navigation

During the flight the FDR did not record any indications as to navigational problems.

The FDR data analysis showed that at the time of the occurrence the aircraft was in

descent at about 11,500 ft PA in Portuguese airspace.

The Portuguese air traffic control unit had not archived the radar recording of the time

of the occurrence; thus it was not available for investigation purposes.

Flight Recorder

Digital Flight Data Recorder:

Manufacturer L-3COM

Model FA 2100

Part Number 2100-2041-00

Serial Number 000196473

Due to the late reporting of the occurrence by the operator, the CVR data of the

occurrence was no longer available. Therefore, no recordings of the radio

communications or the cockpit communications between the two pilots were

available.

The reason mentioned above made it impossible for the BFU to read out the original

FDR data. The operator provided the BFU with the FDR data.

The BFU analysed the data with the Insight Analysis Software. A total of

158:51 hours of recorded flight data was available.

At 1137 hrs the FDR had recorded a bank angle of about 140° to the right and shortly

afterwards a bank angle of about 140° to the left. The two steep turns were initiated

at about 11,400 ft PA.

8 Source: www.Sat24.com


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At 1138 hrs, the FDR recorded the controlled roll about the longitudinal axis of the

aircraft. The flight manoeuvre was initiated with about 286 kt IAS at 11,500 ft PA.

During inverted flight, the aircraft had a speed of about 246 kt IAS and was at about

11,300 ft PA. During levelling off, the aircraft had a speed of about 250 kt IAS and

was at about 11,000 ft PA.

During the flight manoeuvre a load factor of 2.46 g was reached. The roll about the

longitudinal axis of the aircraft lasted about 10 s.

Figure 4 shows the parameters for the analysis of the occurrence:

Indicated Airspeed (IAS)

Roll Angle (deg9)

Pitch Angle (deg)

Engines N1 (% RPM10)

Pressure Altitude based on 1,013 hPa

Vertical Acceleration (g)

Autopilot Activation

9 Degrees 10 Revolution Per Minute


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Fig. 4: FDR data of the flight manoeuvre Source: BFU


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The data of the flight manoeuvre was processed with the InSight Software and

depicted in Figures 5 and 6. Aircraft speed, pitch, bank angle and vertical

acceleration are based on FDR data.

Fig. 5: Illustration of the flight manoeuvre Source: BFU


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Fig. 6: Illustration of the flight manoeuvre Source: BFU


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Figure 7 shows one segment of the flight, based on FDR data, depicted in Google

EarthTM.

Findings on the Aircraft

After the occurrence became known, the maintenance organisation of the operator

performed a technical examination of the aircraft on 17 May 2019. The BFU received

the report of the work performed. It reveals that no damage was found. The following

is an excerpt of the report.

Severe Turbulence and/or Maneuvers Inspection per LJ MM Chapter

05-50-00

No abnormal Indications or deformation found

Elevator Push/Pull Rod removal

Found: LH & RH Rod ends are rejected

Action: Carried out replacement of upper push rods I.A.W. AMM 27-30-

01 Rev ISSUE 14

Fig. 7: Depiction of the flight path Source: Google Earth™, adaptation BFU


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Fire

There was no evidence of in-flight fire or fire during the landing.

Organisational and Management Information

Safety Actions

The operator had described their safety policy in the Operation Manual Part A,

Management System, Chapter 3 of 27.03.2017. Among other things, it described a

procedure to recognise risks. The employees were admonished to report risks in

writing. The operator would treat these reports confidentially. The following is an

excerpt:

[…] Establish and operate hazard identification and risk management

processes, including a hazard reporting system, in order to eliminate or

mitigate the safety risks of the consequences of hazards resulting from our

operations or activities to a point which is As Low As Reasonably Practicable

(ALARP) […]

[…] The Compliance System and the SMS form one unit. All required parts of

each system shall be considered […]

[…] Safety Compliance Policy & Safety Culture Statement; Non punitive policy;

Reporting system, including anonymous reporting […]

Duties of the Co-pilot

The operator had defined the duties of a co-pilot in the Operation Manual Part A,

Chapter Organisation and Responsibilities, Chapter 1 of 27.03.2017. The following is

an excerpt:

In-flight the Copilot shall:

[…] Inform the CMD11 automatically and immediately if something in the

operation of the aeroplane is considered to become abnormal or if deviation

from prescribed procedures, clearances or from the plan of operations

showing up. […]

11 Commander


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Additional Information

Actions by the Operator

The operator promptly released the PIC and the co-pilot from their flying duties and

terminated the employment contract after the occurrence became known.

Similar Occurrence

BFU Report BFU CX001-10

The final report of the investigation comes to the conclusion that the occurrence was

a flight manoeuvre which the aircraft manufacturer prohibited. These pilots were also

not licensed or certified to conduct such a manoeuvre. The flight manoeuvre ended

with the crash of the Cessna 550 B Citation Brave near Reinhardtsdorf-Schöna in the

Sächsischen Schweiz (Saxon Switzerland).

The investigation results in the final report of BFUCX0001-10 determined:

[…]

Investigation Results:

During climb after reaching Flight Level (FL) 270 the crew began to fly a rolling

manoeuvre to the right. During the manoeuvre the crew lost control of the

aircraft, the airplane shot steeply toward the ground and crashed. Both pilots

were fatally injured and the airplane was destroyed.

The accident was due to:

The crew tried to conduct a flight manoeuvre (roll) which is not part of

commercial air transport.

The crew suffered loss of spatial orientation and subsequently did no

longer have the ability to recover the flight attitude.

The following factors contributed

The pilots were not trained in aerobatics.

It was night and therefore there were no visual references.

The relationship between the two pilots resulted in the departure from

professional behaviour in regard to crew coordination.

The airplane was neither designed nor certified for aerobatics

[…]


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Investigator in charge: Norman Kretschmer

Assistance: Bernd Dreyer

Braunschweig 7 Mai 2021

This investigation was conducted in accordance with the regulation (EU) No. 996/2010 of the European Parliament and of the Council of 20 October 2010 on the investigation and prevention of accidents and incidents in civil aviation and the Federal German Law relating to the investigation of accidents and incidents associated with the operation of civil aircraft (Flugunfall-Untersuchungs-Gesetz - FlUUG) of 26 August 1998. The sole objective of the investigation is to prevent future accidents and incidents. The investigation does not seek to ascertain blame or apportion legal liability for any claims that may arise. This document is a translation of the German Investigation Report. Although every effort was made for the translation to be accurate, in the event of any discrepancies the original German document is the authentic version.

Published by: Bundesstelle für Flugunfalluntersuchung Hermann-Blenk-Str. 16 38108 Braunschweig Phone +49 531 35 48 - 0 Fax +49 531 35 48 - 246 Mail [email protected] Internet www.bfu-web.de

18-1808 ub en v02 - final

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