Inertial Friction Welding (IFW) equipment is essential for the welding process of aircraft engine shaft components. However, the absence of comprehensive fault-handling standards for domestically produced inertial friction welding equipment has hindered its further development. This study focuses on the connecting rod and motor of the 30T-IFW equipment, employing a model-based fault detection method. Through simulation, the deformation of the connecting rod and the frequency response of motor vibration acceleration under different working conditions are obtained. Additionally, a monitoring platform is proposed to collect real-time data on connecting rod deformation and motor vibration from actual welding equipment. By establishing a quantitative correlation model of connecting rod deformation-force and revealing the coupling mechanism between motor eccentricity faults and modal frequency vibrations, a hybrid diagnostic framework that combines simulation of primitive warning and measurement of calibration is proposed. At last, the simulation and experimental results verify the effectiveness of the fault diagnosis method proposed in this paper.

Yang, Haifeng, Yuan, Mingqiang, Sun, Tao, Liang, Wu, Gong, Maolin, An, Xingyi, Wang, Qisong, Liu, Dan

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK, CUP WASHER LOCKED, CRES UNS S66286, 130 KSI MIN, .3125-24 UNJF-3A

AS9678D (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, NICKEL ALLOY (UNS N07001) 165 KSI MIN, .2500-28 UNJF-3A

AS9724F (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON, EXTENDED WASHER HEAD, CORROSION- AND HEAT-RESISTANT STEEL, UNS S66286, 130 KSI MIN, .4375-20 UNJF-3A

AS9560A (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, AMS5643 (UNS S17400), 140 KSI, .5625-18, UNJF-3A

AS3173C (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

SCREW, MACHINE - STEEL, DIFFUSED NICKEL-CADMIUM PLATED, DOUBLE HEXAGON EXTENDED WASHER HEAD, DRILLED, UNS K14675, 195 KSI MIN, .1640-36 UNJF-3A

AS9216D (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEX, EXTENDED WASHER HD, PD SHANK, CUP WASHER LOCKED, CADMIUM PLATED, STEEL, UNS G87400, 125 KSI MIN, .1900-32 UNJF-3A

AS9680C (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK, AMS4967 (TI 6AL - 4V), .1900-32 UNJF-3A

AS9750C (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, CLOSE TOLERANCE SHANK, UNS S66286, 130 KSI MIN, .1900-32 UNJF-3A

AS91101E (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - STEEL, DIFFUSED NICKEL-CADMIUM PLATED, DOUBLE HEXAGON EXTENDED WASHER HEAD, UNS K14675, 195 KSI MIN, .3125-24 UNJF-3A

AS9210D (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK AMS5616, .3125-24 UNJF-3A

AS9887B (Current)

8/10/2026

E-25 General Standards for Aerospace and Propulsion Systems

Advancing Reliability Centered Maintenance: A Robust Statistical Approach for MTBF Estimation in Aero-Engine Fleets via Subgrouping Strategy and Dual Weibull Modeling

2026-99-0213

7/31/2026

Fleet heterogeneity, from manufacturing variations and diverse operating conditions, complicates reliability analysis by obscuring true failure patterns in aero-engines. This is a critical challenge in an industry as inaccurate Mean Time Between Failures (MTBF) estimates threaten safety and inflate operational costs, by forcing a choice between inefficiently conservative maintenance or the risk of in-service failures. Conventional analysis often fails by pooling all fleet data. To address this, our paper presents an analytical framework that improves predictive accuracy by filtering, rather than aggregating statistical noise. The methodology uses a Randomized Block Design (RBD) and ANOVA hypothesis test to screen a diverse dataset and isolate statistically homogeneous subgroups. This filtration identifies a core fleet with a consistent failure signature, providing a purified dataset for modeling. This refined data is then modeled using both Weibull and the Exponentiated Inverse Weibull distributions to ensure the results are robust and not model-dependent. Applying this framework to a 25-engine dataset that experienced 66 failures, we isolated a stable failure pattern, yielding a primary MTBF of 171.16 hours and a cross-validated MTBF of 176.35 hours. The close 3% convergence between these models validates our approach. By providing a dependable MTBF, this work establishes a stronger foundation for data-driven Reliability Centered Maintenance (RCM). It empowers maintenance planners to move toward evidence-based intervals, safely extending engine time-on-wing, optimizing spare parts inventory, and significantly reducing direct operational costs for airlines.

Jubaid, Mayin Uddin, Bebe, Gibson, Bigyen, Musa Pethuel, Anik, S M Kullul Mehedee, Yasmin, Ashrafi, Sahran, Mohamed Sideek Mohamed

Effects of Arrangement Patterns on Static Stability and Leakage Characteristics in Hybrid Labyrinth-Honeycomb Seals

2026-99-0166

7/31/2026

In this work, three-dimensional models of axial hole labyrinth-honeycomb seals (AHLHS) and circumferential hole labyrinth-honeycomb seals (CHLHS) were established by CFD to investigate the influence of different arrangement patterns on the static stability and leakage characteristics of two seals under choked and unchoked flow conditions and various eccentricities with different values. The results show that the two configurations have different advantageous ranges, and the hole arrangement pattern will not significantly change the pressure difference distribution between the two seals. Under most studied conditions, AHLHS maintains lower absolute values of stiffness coefficients, pressure difference groove, and negative cross-coupled stiffness coefficients, resulting in higher stability.

Li, Qing’an, Gao, Tongxin, Li, Zeze, Pang, Shuai, Lü, Yanjun, Zhang, Yongfang

BOLT, MACHINE - DOUBLE HEX EXTENDED WASHER HEAD, DRILLED, CLOSE TOL SHANK, AMS5643 (UNS S17400), 140 KSI, .1900-32 UNJF-3A

AS3174C (Current)

7/21/2026

E-25 General Standards for Aerospace and Propulsion Systems

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK, STEEL AMS6322, CADMIUM PLATED, .3750-24 UNJF-3A

AS9917C (Current)

7/20/2026

E-25 General Standards for Aerospace and Propulsion Systems

Procedure for Thermal Aging Test for Polyol Ester Gas Turbine Engine Lubricants

ARP6299A (Current)

7/17/2026

This method is intended to evaluate the thermal and oxidative stability of synthetic, ester-based aviation lubricants under defined conditions of time and temperature. This method is applicable to lubricants meeting the compositional and performance requirements of AS5780.

E-34 Propulsion Lubricants Committee

BOLT, MACHINE - DOUBLE HEXAGON EXTENDED WASHER HEAD, PD SHANK, CUP WASHER LOCKED, CRES, UNS S66286, 130 KSI MIN, .2500-28 UNJF-3A

AS9677C (Current)

7/17/2026

E-25 General Standards for Aerospace and Propulsion Systems

Aircraft Engine–Specific Thrust and Visibility from 2D and Circular Nozzle Exits

2026-01-6003

7/7/2026

In modern warfare, military control of the airspace determines aircraft survivability against the most widespread missile threats. The aero-engine exhaust system is an important source of infrared (IR) signatures from the rear aspect, particularly in the 2–3 μm and 3–5 μm IR bands. Two-dimensional (2D; non-axisymmetric) nozzle exits with high aspect ratio (AR > 5) are widely used in stealth aircraft engines due to their low IR signature, ease in thrust vectoring, and high maneuverability and agility. This analytical study compares the specific thrust (for choked and unchoked flow regimes) and the visible planar areas of a 2D nozzle exit with different ARs with those of a circular nozzle, as seen from the direct rear view. The nozzle’s isentropic efficiency (ηis,noz) is obtained in terms of the total pressure ratio, and the effect of AR on ηis,noz is examined for 1 ≤ AR ≤ 15. It is found that ηis,noz decreases with increasing AR, but this decrease is more rapid in unchoked flow than in choked flow. For the same value of nozzle exit cross-sectional area, the corresponding visible planar areas of aero-engine hot parts are compared for a 2D nozzle exit with different AR with that of the baseline case (circular nozzle), from bore-sight. This study shows that the optical blocking of aero-engine hot parts by a round-to-rectangular nozzle of AR ≤ 4 is almost the same as that of a circular nozzle, from bore-sight.

Baranwal, Nidhi

Helicopter Engine-Rotor System Compatibility

ARP704A (Current)

7/2/2026

This SAE Aerospace Recommended Practice (ARP) recommends a methodology to be used for the design, analysis and test evaluation of modern helicopter gas turbine propulsion system stability and transient response characteristics. This methodology utilizes the computational power of modern digital computers to more thoroughly analyze, simulate and bench-test the helicopter engine/rotor system speed control loop over the flight envelope. This up-front work results in significantly less effort expended during flight test and delivers a more effective system into service. The methodology presented herein is recommended for modern digital electronic propulsion control systems and also for traditional analog and hydromechanical systems.

S-12 Powered Lift Propulsion Committee

Revisiting the Boeing YC-14 and Ball-Bartoe Jetwing USB Powered-Lift Aircraft: Lessons Learned

2026-01-0663

7/1/2026

This paper will revisit an area of Short Take-Off and Landing (STOL) operations and powered-lift aircraft design that has been limited in scope, and at best, very specialized when it comes to research, aircraft built, and experimentation: The Upper Surface Blowing (or USB) aircraft configuration. Five aircraft have been flown successfully using the Upper Surface Blowing powered-lift concept: The Boeing YC-14, the Ball-Bartoe Jetwing, the Antonov An-72, the NASA QSRA experimental aircraft, and the National Aerospace Laboratory (NAL) Aska or Quiet STOL Research aircraft. Only the Antonov An-72 (and its commercial follow-on, the An-74) reached any significant degree of production. This fact illustrates the uniqueness of the USB technology as applied to powered-lift. A background of the technology will be given, what connects them as far as the USB configuration, discuss the main lessons learned, and briefly dwell on other configurations that are close relatives of aircraft using the USB as a source of powered-lift. An extensive review of the existing literature has been fundamental for the development of this paper since many years have passed since the last USB configured aircraft design has flown (the last new USB design to take to the air did so in 1985). Although all the unclassified USB projects that have been constructed and flown will be mentioned in this paper (production and experimental), the main thrust of the paper will be the Boeing YC-14 prototypes and the Ball-Bartoe Jetwing. With respect to NASA’s QSRA demonstrator, the Antonov An-72 series, and the NAL Aska demonstrator, references will be listed for those readers wishing to review the technology and advances made by those aircraft. Their detailed review is beyond the scope of this paper; but the contributions of these aircraft to the state-of-the-art of USB powered-lift configuration is well established.

Pinero, Erasmo

Defining and Measuring Factors Affecting Helicopter Turbine Engine Power Available

ARP1702B (Current)

6/29/2026

This SAE Aerospace Recommended Practice (ARP) identifies and defines a method of measuring those factors affecting installed power available for helicopter powerplants. These factors are installation losses, accessory power extraction, and operational effects. Accurate determination of these factors is vital in the calculation of helicopter performance as described in the RFM. It is intended that the methods presented herein prescribe and define each factor as well as an approach to measuring said factor. Only basic installations of turboshaft engines in helicopters are considered. Although the methods described may apply in principle to other configurations that lead to more complex installation losses, such as an inlet particle separator, inlet barrier filter (with or without a bypass system), or infrared suppressor, specialized or individual techniques may be required in these cases for the determination and definition of engine installation losses. Some rotorcraft may use an alternate source of propulsion system power to supplement engine output shaft power delivered. If RFM performance includes the contribution of a Supplemental Power Unit (SPU), then the installed power available of the SPU should also be defined and measured, for which the power loss factors and methods described in this document may be applicable.

S-12 Powered Lift Propulsion Committee

Evaluation of Helicopter Turbine Engine Linear Vibration Environment

AIR1289A (Current)

6/29/2026

This SAE Aerospace Information Report (AIR) outlines a recommended procedure for evaluation of the vibration environment to which the gas turbine engine powerplant is subjected in the helicopter installation. This analysis of engine vibration is normally demonstrated on a one-time basis upon initial certification, or after a major modification, of an engine/helicopter configuration. This AIR deals with linear vibration as measured on the basic case structure of the engine and not, for example, torsional vibration in drive shafting or vibration of a component within the engine such as a compressor or turbine airfoil. In summary, this AIR discusses the engine manufacturer’s "Installation Test Code" aspects of engine vibration and proposes an appropriate measurement method.

S-12 Powered Lift Propulsion Committee