Railway Investigation Report A11A0101 accessibility page

Figure 1. Control column and bob-weight

A diagram shows the following parts of the elevator stabilizing weight, or bob-weight, system: the bob-weight bellcrank assembly, the link assembly, the bob-weight stop bolt, the link assembly attachment points, and the bellcrank pivot point.

The components are numbered to correspond with their descriptions in the text. The relationship of these components to one another is also described in the text.

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Photo 1.– Bob-weight link assembly

Two side-by-side photographs show the bob-weight link assembly, consisting of the bellcrank and attached weight, and an arrow pointing rightward to indicate the forward (FWD) position.

  • The first photograph shows the correct link orientation.
  • The second photograph shows an incorrect link orientation, in which the bob-weight system's link has gone over centre as described in the text.

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Photo 2.– Bob-weight aligned with damaged area

A photograph shows the bob-weight aligned with the damaged area after being repositioned so that the stop bolt was flexed to the left and the bob-weight was moved rearward beyond its normal range of travel.

An arrow pointing leftward indicates the forward (FWD) position.

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Photo 3.– Occurrence aircraft bob-weight

A photograph shows the bob-weight from the occurrence aircraft, with multiple imprints caused by the stop bolt.

The imprints begin near the edge of the bob-weight and extend over the edge and down the side for about 1 inch.

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Photo 4.– Damage to C-CPCY

A photograph shows damage to the aircraft's bob-weight system that is consistent with the stop bolt scraping along the surface of the left side of the weight.

The aft surface of the bob-weight bellcrank support structure is deformed rearward, and the stop bolt is aligned close to the left edge of the bob-weight.

An arrow pointing leftward indicates the forward (FWD) position.

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Photo 5.– Model Communiqué #91 images

Two side-by-side photographs from Model Communiqué #91 show

  1. the operator's bob-weight stuck on the stop bolt, and
  2. another bob-weight that had contacted the stop bolt on the left side of the weight.

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Appendix B. Hawker Beechcraft Corporation Model Communiqué #91

Airliner 1900 Series

Communiqué # 91 (page 1)
January, 2010

ATA 27 - Elevator Stabilizing Weight Installation

Recently Hawker Beechcraft was notified by an Operator that one of their aircraft had a discrepancy with the flight controls.

“When taxiing to the runway, the pilot tried to perform his normal flight control checks but was forced to return due to the elevator controls being stuck in the full nose down position”.

During maintenance troubleshooting the discrepancy was discovered. The elevator stabilizing weight P/N 101-524143-3 had traveled past the stop bolt P/N NAS428-4-20 (ref. Figure 1).

Figure 2 shows another stabilizing weight with only partial contact of the stop bolt.

The stabilizing weight or “bob weight” is incorporated into the elevator control system for improved stability and weighs in at 19.25 +/- .25 pounds. There are cautions within the Maintenance Manuals advising the end user to not allow the control column to free fall to the down position. The first sentence of the caution says “Carefully lower the elevator surface”. The last sentence states “This could cause damage to the elevator system”.

While these cautions and warnings within the publications seem mundane, there is considerable amount of effort involved in creating each and every one.

The Operator that reported this incident stated “We believe this problem is caused by the elevator control column being pulled back (when the aircraft is on the ground) and then being released. This causes the elevator control to slam forward and the momentum of the bob weight causes it to impact the stop, bending the bracket and/or the stop bolt”.

HBC wants to remind Operators that an occurrence of this nature can happen if the maintenance practices are not followed. This would include all notes, cautions, and warnings.

If your aircraft is stored or parked outside, HBC recommends installing control locks. These locks are called out within the Maintenance Manual publications in Chapter 27. Also when using the locks reference Safety Communiqué SC01. This document was re-released in March, 2008.

Communiqué # 91 (page 2)

2 images are displayed

  1. Figure 1 — Stop Bolt Caught on Weight
  2. Figure 2 — Partial Contact Noted on Weight, Forward of Stop Bolt

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Appendix C. Hawker Beechcraft Corporation Safety Communiqué #321

Safety Communique (page 1)

December 2011

TO:

ALL OWNERS AND OPERATORS, HAWKER BEECHCRAFT SERVICES,
CHIEF PILOTS, DIRECTORS OF OPERATIONS, DIRECTORS OF
MAINTENANCE, ALL HAWKER BEECHCRAFT AUTHORIZED SERVICE
CENTERS, AND INTERNATIONAL DISTRIBUTORS AND DEALERS.

MODELS:

All 1900 Models, Serials UA-3; UB-1 through UB-74; UC-1 through UC-174;
UD-1 through UD-6; UE-1 through UE-439.

SUBJECT:

REPORT OF ELEVATOR CONTROL RESTRICT

Hawker Beechcraft Corporation (HBC) has received two (2) reports of the elevator control system having limited nose-down control during takeoff. In this system, link assembly P/N 101-524112 connects the control column to the elevator bob-weight bellcrank. This link assembly, in each case, was reported to be overcenter, thereby restricting elevator travel.

2 images are displayed:

  • Image 1 shows the correct link orientation
  • Image 2 shows the incorrect link orientation

Safety Communiqué No. 321 (1 of 2)
The export of these commodities, technology or software are subject to the US Export Administration Regulations. Diversion contrary to U.S. law is prohibited. For guidance on export control requirements, contact the Commerce Department's Bureau of Export Administration at 202-482-4811 or at www.bxa.doc.gov.

Safety Communique (page 2)

The overcenter condition may be facilitated by a misrigged secondary stop and/or excessively worn components in the elevator control system. One report revealed damage to the P/N 114-524061-21/-35 support structure containing the elevator bob-weight, allowing additional travel of the bob-weight.

1 images show

  • Bellcrank/Bob-Weight Damage

The second report revealed an elongated bob-weight bellcrank pivot hole in the P/N 114-524061-35 support structure. Therefore, it is important to inspect all associated components for any abnormal wear or conditions per the requirements in the Maintenance Manual (MM), Chapter 5.

If rigged correctly, the elevator control bob-weight will have a 0.56 +0/-0.12 (0.44 to 0.56) inch clearance to the stop bolt when resting on the down elevator primary stop.

If the airplane is parked or moored outside, control locks must be installed as described in the MM. When using the control locks, refer to Safety Communiqué No. 1, which was re-released in March of 2008. Airliner 1900 Series Model Communiqué No. 91 stresses the importance of using control locks and following all cautions and warnings in the MM, and includes the following statement: “CAUTION: With the control column pulled to the aft position, allowing the control column to free-fall to the forward position can cause damage to the elevator system.”

Mandatory Service Bulletin 27-3739, Flight Controls - Flight Control Column Link Assembly Inspection/Modification, provides instructions to inspect the link assembly and modify the installation to prevent the bearing from separating from the link assembly.

Application of proper elevator control system rigging, parking and mooring procedures, as defined in the MM, is essential to ensure that the system operates as designed. Proper application of defined airplane parking and mooring procedures ensures that the system is protected from abnormal forces, such as jet blast, wind gusts, or improper handling.

HBC has performed testing on the Model 1900 elevator control system and could not duplicate the reported condition. For technical questions, please contact Hawker Beechcraft Corporation Technical Support at 1-800-429-5372 or 316-676-3140.

Safety Communiqué No. 321 (2 of 2)
The export of these commodities, technology or software are subject to the US Export Administration Regulations. Diversion contrary to U.S. law is prohibited. For guidance on export control requirements, contact the Commerce Department's Bureau of Export Administration at 202-482-4811 or at www.bxa.doc.gov.

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