Next Generation — Articles / Posts — Flaps 2 Approach

Lower electrical panel showing reproduction latex-style cap (ELEC 2) and OEM Honeywell Switch Accessory 15PA90-6W (ELEC 1). For those with keen eyes - yes that is a voice recorder in the lower panel - more to follow in later posts. Of interest are the two different white caps (read main text)

It has taken a very long time to collect the assortment of OEM needed parts to complete the forward and aft overhead panels. Finally the build is now in progress and it’s hoped completion will be towards the end of 2016.

OEM Overhead Panel Switches (2 main types)

There are two main types of switches used on the forward and aft overhead panel. The push/throw switches (Honeywell switches pictured above) and the normal toggle-type switches. The Honeywell switches use a screw on white cap while the standard toggle switches use use a condom style white cap.

Honeywell Switch Accessory 15PA90-6W showing internal screw thread. The thread screws onto the stem of the toggle switch

Anatomy of the OEM White Cap

The Honeywell switch caps are not a slip-on latex cover but a solidly-produced head with an internal aluminium thread. The head is designed to be screwed directly to the shaft of the toggle switches. Firmly attached to this head is the white latex cap. This is the cap that is used on the push/throw switches.

Reproductions

Most of the reproduction white caps for the push / throw switches are either push-on style condoms, or a white-capped head attached to a slender hollow shaft. The shaft then slides over the existing switch stem.

The reproduction slip-on caps currently available on the market bear little resemblance to those made by Honeywell.

Important Point:

Bear in mind that the push / throw switches are used regularly and are usually forcefully manipulated; many reproductions do not stand up to continued abuse.

Choice - so many options

I had purchased several dozen OEM Honeywell toggle switches, however, for whatever reason the white caps on the toggles were either missing or damaged. Honeywell OEM switches are not inexpensive, so I was going to use reproduction white push-on caps (aka white condoms), but the caps failed to fit snugly to the OEM switches, and their appearance was slightly different to the OEM version - the ends of the caps looked rather bulbous.

My next choice was to use latex caps that are used in automotive industry. Once again, the appearance was slightly different and the automotive caps sported a small nipple at the end of each cap where they had been connected to the plastic retaining spur; I found the appearance of the nipple disconcerting.

Short of viable options, I purchased the OEM white caps from Honeywell which is the company that supplies Boeing. If you carefully look at the above picture of the lower electrical panel (click image to enlarge picture), you will observe the nearest toggle switch has been fitted with an automotive style cap; the nipple and joining line is clearly visible. The second toggle switch is fitted with the Honeywell white cap.

Installing the White Toggle Cap

To mount the white cap to a Honeywell switch you must first gently heat the switch stem. The heat will loosen the head of the toggle. It then is an easy matter to screw off the head and replace it with the OEM head. To heat the stem use either a hair dryer or paint dry gun (used to dry paint).

Measurements

Not everyone wants to utilise OEM parts. As such I have provided the measurements of the switch head (courtesy of Honeywell) for those who wish to try their hand at making their own white caps.

If you are searching for the other style of white caps used on the standard toggle switches, the part number for the correct condom white cap is 69-44578-2.

Reproduction Condoms - suppliers

For those not wishing to use OEM, there are several companies that manufacture reproduction white toggle caps. For example, PC Flights and GLB United Kingdom.

For further information see an earlier article: Toggle Condoms.

Glossary

Honeywell – Avionics conglomerate that is heavily involved in the defense and aviation industries.
OEM – Original Equipment Manufacture.

There is little mistaking the tell-tale white-coloured handles and skirts of the Next Generation Throttle

The advent of high quality reproduction parts that marry with advanced avionics suites, such as ProSim-AR and Sim Avionics, has led many flight simulator enthusiasts to strive closer to Microsoft’s claim ‘as real as it gets’.

The availability of OEM parts formally used in classic airframes has never been greater, and many enthusiasts are purchasing various parts and converting them to flight simulator use.

The ‘holy grail’ of conversion has always been the Boeing throttle unit, and depending upon individual requirements, many older style throttle units have been retrofitted to appear very similar, if not near-identical, to their Next Generation counterparts.

This article will compare and contrast the major differences between the Boeing 737 classic throttle and the Next Generation throttle. The word classic is usually used to refer to airframes belonging to the 200, 300, 400 and 500 series. The Next Generation (NG) refers to the Boeing 600, 700, 800 and 900 series.

Boeing 727-100 throttle quadrant. Although there are obvious differences in that the 727 has three engines, the overall design and appearance of the quadrant is very similar to its modern counterpart. Image copyright to Keven Walchle

Historical Context

The throttle quadrant observed in a modern airliner has relatively old roots.

The fore bearer of the Next Generation throttle was designed in the late 50's and early 60's and was initially used in the Boeing 707 airframe. As aircraft types evolved, throttle design remained relatively static with similar-designed throttles being used in the Boeing 727, 717 and 737 series aircraft.

The B737-100 made its debut in April 1968, to be followed shortly by the 200 series with a slightly longer fuselage. During the 1980’s Boeing released the classic series of airframes (300 through to 500 series).

During this time, the technology altered little and the design of the throttle quadrant reflected the ability of Boeing to reuse existing technology with minimal alterations. This principle of reuse can save a company millions of dollars in redesign and development costs.

This Goes With That (Compare and Contrast)

The Boeing 737-800 Next Generation is the airframe that many enthusiasts strive to duplicate in a flight simulator. The reason for this two-fold. First, the Next Generation is the most umbilicus aircraft flown today, and second, the availability of software that mimics the avionics suite in this aircraft.

However, Next Generation parts are difficult to find, and when found are expensive to procure. Fortunately for the simulation community, a throttle will function correctly in flight simulator no matter what airframe the throttle originated.

Many of the nuances between a classic and Next Generation throttle quadrant are subtle, and for the most part only the more knowledgeable will notice.

The more obvious highlights of the Next Generation are the white-coloured thrust lever shrouds, TOGA button assembly, détentes flaps arc, speedbrake lever knob, and the moulded white-coloured side panels and panniers of the lower part of the throttle unit. Whilst it's possible to alter many of the attributes of a classic throttle to conform with those of an Next Generation, not every part can be easily transformed. For example, the flaps détentes arc between the classic and Next Generation is very different in design and appearance, and cannot be altered.

TABLE 1: Overview to the main visual differences between the classic and Next Generation throttle quadrants (courtesy Karl Penrose who kindly allowed the use of photographs taken of his 600 series throttle). Note that there may be other subtle differences, some visual and others in design/operation.

The table doesn't address the center pedestal as pedestals vary greatly between airframes.

Retrofit refers to the level of difficulty it is to make the classic throttle appear similar to the Next Generation. Yes meaning it is possible and no, for the most part, meaning it is not possible.

**TABLE 1:** an overview to the main visual differences between the classic and Next Generation throttle quadrants

1Erratum: The trim wheels on the Next Generation are slightly smaller in circumference to those of the Classic series.

2 The words 'level of difficulty' is subjective; it depends on numerous factors such as experience and knowledge – neither of which is identical between individuals.

Important Point:

By far the most challenging hurdle during a Next Generation refit is the the alteration of the throttle lever shrouds and the TOGA button assembly.

Final Call

The differences between a classic and Next Generation throttles are largely cosmetic with some subtle design and operational differences. Retrofitting a classic throttle to appear similar to a Next Generation throttle is possible. However, there will be some things that probably won't be altered, such as the speedbrake lever handle, stab trim indicator tabs, side mouldings, panniers and flap détentes arc.

This said, the ability to use an OEM throttle, no matter from which airframe, far supersedes any reproduction unit on the market. OEM throttles are sturdy, robust and well-built. Unless you do something particularly foolish, you won't damage an OEM throttle.

BELOW: Two image galleries showing the various differences between the classic and Next Generation throttle quadrants. Thanks to Karl Penrose who kindly allowed the use of photographs taken of his 600 series throttle. To stop the slideshow, click the image and navigate by the numbered squares beneath the image.

Boeing 737 Classic Series Throttle Quadrant

737-400 Throttle Quadrant (note T-Lockers)

Overall view of a 500 series throttle unit

B737-500 bare metal levers and TOGA box assembly

Classics have a bare metal box that houses the TOGA buttons

B737-300 speedbrake knob

Chunky appearance of speedbrake knob

B737-500 backlighting

Backlighting is incandescent (bulbs) on all units prior to the NG.

B737-500 Stab Trim Indicator Needle

The classics have a very chunky white painted metal indicator needle.

B737-500 Stab Trim Indicator Needle

The classics have a chunky white painted metal indicator needle.

B737-500 uneven flaps detente arc

Uneven flaps detente arc

B737-500 Stab Trim Toggle Assembly and T-Lockers

The stab trim toggle assembly is one of the items on later classic throttles that is identical on the NG throttle.

B737-500 Throttle Quadrant and Bare Metal Paddle-Style Stab Trim Indicators

The 100, 200, 300 and some 400 series throttles used paddle-type stab trim indicators. There is some overlap between the use of the paddles and the NG style T-Lockers.