Occurrences December 2021 - January 2022
During a cross-country flight, the pilot inadvertently flew through restricted airspace – outbound the pilot flew through R265F, and inbound he flew through R265B, R265E and R234.
On the outbound leg the glider had a 20kt tailwind and covered ground quickly. However, on the return leg the pilot struggled make headway into this wind and he began to press on with little or no margin. Fatigue was affecting the pilot’s decision-making and his navigation. While climbing in a thermal the pilot realised that he was inside restricted airspace and turned to track out of the airspace. However, the pilot did not clear the restricted airspace before turning towards the home aerodrome. In a post flight debrief with the CFI, it was identified that in a high workload environment the pilot tended to become fixated on problem solving to the detriment of situational awareness. The pilot agreed to conduct a flight review of his review his airmanship and decision-making processes prior to flying in command and undertook retraining in airspace procedures.
Situational awareness is having an accurate understanding of what is happening around you and what is likely to happen in the near future. By being aware of what is happening around you and understanding how information, events and your own behaviour will affect your own goals, you have situational awareness. Having situational awareness doesn’t happen by accident, it is a cognitive skill. You need to build and maintain situational awareness to ensure that you are able to stay ahead of a situation and avoid being caught off guard or unprepared. To build a mental model of the environment, it is necessary to gather sufficient and useful data by using our senses of vision, hearing and touch to scan the environment. We must direct our attention to the most important aspects of our surroundings and then compare what we sense with the experiences and knowledge in our memory. It is an active process and requires significant discipline, as well as knowing what to look for, when to look for it and why. For further information, refer to skybrary.aero/articles/situational-awareness.
Phoenix Air U15
GFA Investigation (Findings reported to the ATSB)
On 29 December 2021 at approximately 14:45 AEDT, the U15 Phoenix touring motor glider registered under CASR Part 47 departed the Benalla, Vic CTAF on cruise-climb, passing through 3500 ft and around 90 knots when the autopilot was engaged. The aircraft pitched forward and accelerated up to, and briefly exceeding, Vne (120 knots TAS) before the acceleration was arrested by a pull-up performed by the pilot overriding the autopilot. A rapid succession of bangs was heard, with a louder final bang at some point during this overspeed sequence approximately 4 minutes into the flight. The pilot continued the flight to Merimbula NSW. After landing and disembarking, the pilot noticed that the fuselage tail boom near the vertical stabiliser junction had experienced a major structural failure. No injuries resulted from the incident. The cruise-climb, at high speed and engine RPM, made the aircraft more vulnerable to pitch-related overspeed than it would at the recommended climb-cruise speed. The high airspeeds encountered beyond the maximum manoeuvring speed, maximum structural cruise speed and marginally beyond Vne, coupled with elevator inputs and clear air turbulence, are the probable contributing factors in the structural failure. The U15 Phoenix is closely related in empennage design to other types that have a history of similar in-flight structural failures. A preliminary report was provided to the Civil Aviation Safety Authority.
Injuries to persons
The pilot was uninjured.
Damage to aircraft
The aircraft was substantially damaged, suffering a full skin thickness fracture of the tail boom just forward of the position where the leading edge of the vertical stabilizer intersected the fuselage. The fracture extended about 70% around the circumference the tail boom (refer Figure 2)
Manufacturer:Phoenix Air s.r.o.
Country of manufacture:Czech Republic
Year of manufacture: 2013
Engines:One - Bombardier Rotax Ltd, 912 ULS
PropellorWoodcomp 2 Blade Feathering
Total airframe hours:325 hours
Total Engine Hours:301 Hours
Certificate of Airworthiness:Yes, perpetual
Maintenance ReleaseYes, until 18/08/2022
The U15 Phoenix is a special light sport aircraft (S-LSA) touring motor glider that is a derivative of the Urban Air UFM-13 Lambada. The U15 Phoenix was developed and initially manufactured by Phoenix Air s.r.o. in the Czech Republic. The current manufacturer and licence holder is Pure Flight in the Czech Republic
(https://www.pure-flight.eu). The Phoenix is a single engine, carbon airplane with two side-by-side seats. The airplane is equipped with a fixed main wheel undercarriage with a steerable tail wheel. The fuselage is a carbon shell with carbon/kevlar seats integrated. Safety belts are attached to the seats and to a shelf intended for lightweight objects (headphones, maps, etc.). The wing spar is carbon and the wing is a monospar construction with a sandwich skin composed of two layers of fiberglass with a foam core. Control surfaces are of the same construction. The airplane is controlled by a dual push-pull control system, only the rudder drive is controlled by cable. The ailerons and elevator are controlled by the control stick located
It is unclear whether the Dynon SkyView system incorporates calibration of airspeed sensors; consequently, it is unclear as to whether the Indicated Airspeed (IAS) and TAS data presented to the pilot and recorded in the flight log adjusts for static pressure errors. Noting that the IAS under-reads compared to Calibrated Airspeed (CAS), this suggests that actual TAS values encountered may have been higher than those presented in the flight records. Due to the low wind speeds and operating height of the aircraft above mountainous terrain, orographic gust conditions such as rotor is unlikely to be a factor in the incident. However, based on the conditions experienced by gliders operating in the area at the time, there is a strong potential for encountering up to 7 m/s thermal updrafts. These conditions cannot be regarded as `very smooth conditions’ required for safe engagement of the autopilot. Likewise, the aircraft airspeed was in excess of the maximum structural cruising speed (Vb) at the time of the incident, so it is plausible that encountering clear air turbulence resulted in structural failure. However, the flight records do not indicate a severe loading (the maximum acceleration was 2.5 g). During the incident, the aircraft was flown well in excess of the maximum manoeuvring speed (Va) and the combination of pitch inputs by the autopilot and command pilot (during the override pitch-up) may have resulted in elevator inputs that were high magnitude or sufficiently abrupt to overload the airframe. Again, though, because the flight records do not indicate a severe loading (maximum acceleration or pitch rate), this is an unlikely cause of failure.
It is unusual that in the U15 Phoenix Aircraft Operating Instructions, the Va and Vb speeds are expressed in TAS rather than IAS — this is most likely because flutter limits are based on TAS at all attitudes. During the incident, the aircraft exceeded Vne and may have experienced symmetric or asymmetric flutter that overloaded the structure at the tail-boom to vertical stabiliser junction. The excess of airspeed beyond Vne was within the type’s design tolerance for demonstrated flutter speed. There is insufficient data to determine whether the structural damage occurred entirely during the first overspeed event, or if the cracks extended during the flight after this event.
About four minutes into the flight the pilot experienced the flutter event that was accompanied by loud banging. The pilot “wondered if the rudder felt normal so slowed and did a few turns and decided the rudder behaved normally”. The pilot then reasoned that the subsequent “…need for right-rudder in the cruise (was due to their) first experience cruising with the Autopilot.” The pilot rationalised that the flight could be continued, despite a flight time to the destination of nearly 2 hours over known rough high country, and with the departure airport close by. This sequence of events fits a well-known pattern in human factors, called plan continuation, when the decision to continue to the planned destination or toward the planned goal is made despite significantly less risky alternatives existing, such as landing at the nearest airport. Plan continuation is also known as goal fixation, get-home-itis, press-on-it is and hurry syndrome. Decision-making in complex, dynamic settings is hardly about making decisions, but rather about continually sizing up the situation. The ‘decision’ is often simply the outcome, the automatic by-product of the situation assessment. This is what turns a decision on whether to continue with a plan into a constantly (re-)negotiable issue – even if the decision is not made on the basis of an assessment of the situation now, it can be pushed ahead and be made a few or more seconds later when new assessments of the situation have come in. The order in which cues about the developing situation come in, and their relative persuasiveness, are two key determinants for plan continuation. Conditions often deteriorate gradually and ambiguously, not precipitously and unequivocally. In such a gradual deterioration, there are almost always strong initial cues that suggest that the situation is under control and can be continued without increased risk. This sets a pilot on the path to plan continuation. Weaker and later cues that suggest that another course of action could be safer have a hard time dislodging the original plan. In summary, plan continuation means sticking to an original plan in rapidly evolving situations, while the changing situation calls for a different plan: Early cues that suggest the initial plan is correct are usually very strong and unambiguous. This helps lock people into a continuation of their plan. The persuasive early cue here would have been the aircraft behaving relatively normal post incident after the pilot conducted a basic assessment of the aircraft’s stability.
- Later cues that suggest the plan should be abandoned are typically more ambiguous and not as strong. These cues, even while pilots see them and acknowledge them, often do not succeed in pulling pilots away from the plan. In this case, a later cue would have been the need to use continuous right rudder in the cruise.
While there is insufficient data to determine whether the failure was caused from static overloading or from flutter, it is more likely than not the incident was the result of flutter caused by high magnitude elevator inputs by the pilot during one or more overspeed events during flight in turbulent conditions.
The following findings are made
1 The command pilot was certified and qualified for the flight in accordance with existing regulations.
2 The maintenance records indicated that the aircraft was equipped and maintained in accordance
3 The centre of gravity of the aircraft was within the prescribed limits.
4 The aircraft mass was within MAUW limits.
5 The autopilot was engaged in conditions beyond the stated operating limits of the airframe,
resulting in pitching down and acceleration beyond Vne. The cruise-climb at high speed and engine RPM made the aircraft more vulnerable to pitch-related overspeed than it would at the recommended climb-cruise speed.
6 The high airspeeds encountered beyond the maximum manoeuvring speed, maximum structural
cruise speed and marginally beyond Vne, coupled with elevator inputs and clear air turbulence resulted in structural failure.
7 Subsequent periods of flight at high speed with already damaged structure may have extended the
damage, though there is insufficient data to establish whether this is the case.
The following recommendations are made:
1 The status regarding the airworthiness of the U15 Phoenix with respect to flutter with the older tail
design inherited from the UFM-13 Lambada should be investigated. Likewise, the status of other UFM-13 derived designs such as the Distar D-13-15 Sundancer should be investigated.
2 Pilots to be advised when an inflight event results in observable changes to the aircraft handling characteristics, the flight should be aborted immediately.
3Safety features in autopilots, such as maximum airspeed settings, should be employed to offer
additional protection from autopilot-induced overspeed.
4 The GFA raise pilot awareness of the flight envelope to enhance their understanding of flutter and
the circumstances that can lead to this phenomenon.
While local soaring, the pilot flew across the Class C airspace boundary and infringed the CTA by two thousand feet vertically and 1.5 kms laterally. After a couple of minutes the pilot realised his error and promptly exited the airspace.
The pilot self-reported the infringement and submitted a trace to the club Airspace Officer. A temporary loss of situational awareness was the main factor in this airspace infringement. The pilot was counselled and lost command flying privileges pending retraining.
Violations of controlled airspace can be avoided by remaining situationally aware, ensuring you have current airspace charts, and by thoroughly familiarising yourself with local airspace and other aeronautical issues. In flight a pilot should always know their position relevant to the controlled or restricted airspace steps. Using an electronic flight bag with a moving map will help you keep a track on where you are in relation to controlled airspace. Pilots should create a buffer of, say, 2 nm from the edge of controlled airspace and 200 feet above (or below).
The pilot was returning home from a 500km out and return flight after five hours. The pilot reported soaring conditions were good and the glider encountered a lot of lift during the final glide. The pilot made a detour to the West and inadvertently flew across an airspace boundary into controlled terminal airspace. The pilot noted his error and immediately tracked out of the area.
The club Airspace officer reviewed the pilot’s logger trace and determined that the pilot had flown across the airspace boundary by 2.1 kilometres and about 600ft above the Class ‘C’ airspace lower limit. The CFI noted that the pilot failed to maintain sufficient situational awareness. The pilot was counselled and undertook remedial training on airspace procedures.
A violation of controlled airspace occurs when a pilot enters controlled airspace without a clearance. Unauthorised aircraft in controlled airspace present a potential collision threat to other aircraft. There are several ways to avoid controlled or restricted airspace:
After returning to the aerodrome from a cross-country flight, the pilot configured the aircraft for landing and then confirmed the undercarriage was down and locked during the pre-landing checks. The glider bounced on touchdown and as it settled back on the runway the undercarriage collapsed.
Subsequent inspection at an approved maintenance organisation identified that a critical part of the undercarriage mechanism broke on touchdown, causing the undercarriage to retract. It was determined that either a heavy landing or a series of heavy landings over time had weakened a part of the mechanism, which eventually failed.
Fatigue is a common occurrence among all metal components of an airframe. Due to the repeated flight cycles and frequent use, the metal elements of undercarriages can become weakened over time, and they will eventually require attention and repair. This weakness manifests in cracks, which are microscopic at first. With continued aircraft use over time, the cracks grow larger and eventually become visible. The detection of premature failure of components depends on sound inspection techniques and inspector awareness. Non-destructive testing methods are well proven ways of finding fatigue cracks. For further information, refer to GFA Basic Sailplane Engineering.
1- Jan- 2022 nswga
The self-launching sailplane had taken off from RWY 36 and was established in the climb with the engine at about 6000 RPM. At around 3,000ft QNH about 7 NMs from the aerodrome, the command pilot handed over control to the second pilot. Shortly thereafter, the command pilot observed the engine RPM drop to 3000 RPM (idle) and assumed the second pilot had throttled back. However, this was not the case and the engine soon stopped. The command pilot assumed control, turned back towards the aerodrome, and attempted to restart the engine, both with the starter and by increasing speed, to no avail. The command pilot then found he was unable to position the propellor to manually retract it. The command pilot made a broadcast on the CTAF advising of the engine failure and that he was returning to land on RWY 36. After joining a short base leg, the command pilot made a successful landing.
Investigation by an approved maintenance organisation found the engine failure was caused by the collapse of the big end bearing in the rear cylinder, pieces of which passed through engine. A possible cause of the collapse was a lack of lubrication, despite the engine being operated in accordance with the Aircraft Flight Manual and having computer-controlled fuel injection. The engine has only 47 hours of operation, and similar problems have been identified with low hours engines of the same type overseas. The aircraft operator is in discussion with the aircraft and engine manufacturers.
Safe operation of any powered sailplane is dependent on the reliability of the aircraft’s propulsion system. Unfortunately, the design standards do not require an acceptable level of reliability for sailplane engines so they should always be treated as unreliable. An engine failure after take-off is an obvious risk area, especially so until the aircraft is high enough to return to the airfield. Consideration should always be given to landing options during climb out. Suitable landing options (paddocks) should be assessed until the aircraft is in a position to return to the airfield. Planning beforehand is always better than trying to make a plan after the engine has malfunctioned.