Airtest – Rockwell 840

Bethany fields a number of good reasons why corporate flying should switch to Rockwell’s new series:

• Wing treatment: a new drag-efficient 52.1ft wingspan featuring new-era winglets designed to discipline airflow. Faster cruise is claimed with this new wing without increasing fuel consumption. Props; Rockwell commissioned the designing of state-of-the-art supercritical type props, reducing drag out towards the tips. Dowty Rotol eventually came up with longer prop life, lighter weight and low vibration levels in their custom-made prop design.

• Fuel system: Rockwell’s wet wing outboard of the nacelles increases tankage and range – enough for nearly all average business trip distances in Australia with only one stop east to west. There’s a simple gravity-feed fuel system, accurate fuel supply monitoring using sensors and a digital fuel tote. Fuel booster pumps are readily available for servicing, not buried in the tanks.

• Design research: Rockwell’s Bethany design team did extra homework in optimising in-flight stability around the pitch and roll axes, while the long tail arm ensures yaw stability.

• Engines: After pioneering the use of AiResearch motors on earlier model Commanders, Rockwell installed the AiResearch TPE331 dash 5 in the 840 Jetprop Commander, rated at 840 THP – hence the 840 label for what’s really the 690C.

Engines are limited identically for take-off and maximum continuous readouts – 71 7.5 shaft horsepower, 100 per cent revs (1591) and interstage turbine temperature (ITT) at 923C.

There are of course the usually-expected attributes in the buyer’s list – new low-drag engine nacelles, power nosewheel steering, power brakes and corrosion-proofing throughout the structure before assembly.

All the points add up to a pretty magnificent aircraft, aimed with unerring marketing clout at the executive market by Civil Flying Services Pty Ltd.

The first Jetprop Commander 840 in Australia, still wearing its US registration of N5871K, has attracted more than just polite attention during its so-far limited demonstration exposure in the region. In fact, a South-East Asian customer has already put a deposit on Seventyone Kilo, says CFS Marketing Manager Norman St John. His colleague, Sales Manager John Burns, who flew a lefthand seat during AADR’s evaluation, backed up this optimistic tact by stating that the type had already been the subject of some searching and approving study by Australia-based leads.

We aren’t surprised; the 840 is a sound business aircraft, no matter at which end one sits and operates. The cockpit is a pure businesslike environment, while the cabin is quiet enough to really work in, to discuss business matters in flight. Fatigue is almost a non-event in the 840.

The aircraft evaluated, brought to Sydney tor AADR by CFS, was the first in Australia, as mentioned. She bore Serial 11619 and came off Bethany’s production line last February, according to her Manual.

At first glance, N5871K looked very much like mos1 Commanders, apart from those Space-Age winglets and those clean, clean lines of nacelles housing a brace of Garret 331 dash Fives.

On closer acquaintance, however, it was apparent that Bethany’s cleanup job on the airframe and wings was really something different.

Finish equalled the excellence of streamlining and drag elimination on the evaluation aircraft, during a walkaround at Sydney airport. The interior finish was likewise excellent. The 840 can be ordered in an 11-seat configuration, but the test aircraft was fitted out in club style – eight seats all told, excluding the loo.

Among the changes worked was a wonderfully large picture window in the main cabin – huge and capable of standing up to the 5.4psi pressure differential at operating height. One often hears the overworked word luxury used in cabin descriptions. In the 840’s case, it under-stated the case … Nett result – an airy, light cabin, superbly appointed in either and fabric, low in decibels and high in creature comforts.

A full 70ft baggage compartment aft is padded, carpeted and lit, with insulation and electric heating available. A 600lb load limit is placed on the baggage compartment.

In the main cabin, each passenger has individual lighting, heating, cooling and ventilation nearby, no matter where he/she sits.
In the cockpit, it’s obvious that Rockwell has done their design homework well and almost unobtrusively. The panel boasts a full range of avionics, some digital, such as DME readout and ground speed interpretation, while weather radar is available. Collins’ autopilot does most of the work en route and does it wonderfully well without snatching.

Ram’s horn controls the front in the lefthand seat – flight instruments, auto-pilot, VOR and other electronics. The centre panel is taken up by engine instruments and fuel management gauges.

Commander controls sit just under a coaming-up annunciator panel, with repeat flight instruments on the righthand side. Rockwell’s Commander series overhead panel standard fitting in the new 840 as far as siting goes.

The entire array is one of workmanlike control without too many unnecessary gimmicks or superfluous indications. As Bethany claims, all instruments are visible (with a little bobbing bout) from either crew position, as are all controls and witches. There is up to 10-mode switching on the control wheel if you want it. And of course, there is the usual and much-envied Commander-style vision from the front office – wrap-around windows and eyebrows.

The sum total asking price for the evaluation aircraft is, according to CFS, around $985,000. And AADR feels this is a good investment.

We digested limitation figures before lighting the Garretts and requesting taxi clearance. Numbers include: Va (manoeuvring) 137kts IAS at 10,3251b; 133kts at 10,000Ib, and 111kts for 7,000lb. Vfe, 20 degrees to half flap 178kts, 40 degrees to full flap 141kts. Vlo and Vie are similar at a very high and workable 198kts indicated. Vmca 93kts IAS. Mmo (limiting Mach number) 0.52. Vmo at 19,000ft 240kts, and 186kts at 31,000ft.

It was apparent – and proved in our evaluation sortie – that these numbers added up to a workable aircraft in the APT environment of primary airports and approaches, and provided a fast transportation tool for businessmen in a hurry.

Engine start was surprisingly simple when using the checklist; negative torque sensing checks, monitoring ITT, hydraulic pressures and other vital items preceded taxying.

ITT Start limit was 1149C, and hydraulic pressures were between 900-1075psi. Commanders were pre-set and cabin pressurisation was dialled in for Flight Level 210.

With six pob and 1000Ib of fuel in each tank, we were at about 9020Ib – well under the maximum take-off weight of 10,3251b – as we lined up. The outside air was +16C, with a wind of 230/15 gusting to 20kts on Runway 25.

Cleared for a radar departure on heading 310 to 3000ft, power levers were advanced against brakes after final checks.

Acceleration was brisk and swift, with Vmc gone and forgotten in an instant. Ground roll with zero flaps is listed as 1285ft, but the evaluation aircraft left the deck in far less, climbing enthusiastically at an initial 1 500fpm, gear coming up with minimal pitch change.

With 135kts pegged to the dial, 71K increased rate of climb to 2000fpm, then 2600fpm, rpm remaining steady at 96 per cent.

Flight planning called tor tracking to Aeropelican, thence to McQuoid and back to Sydney. Our first real batch of readouts at 9000ft returned 130kts IAS, outside air coming down from +12C, 900 ITT and an ascent rate of 2000tpm with revs still steady on 96 per cent.

The Jetprop Commander 840 sat as steady as the proverbial rock despite some initial chop. Noise levels were low enough to make low-voice conversation possible in the cockpit, and hear similar conversation in the main cabin.

The Collins was switched in at about the time we took our next readings; 132kts IAS, DME at 18.3 miles out of Sydney, climbing at 1800fpm, and fuel flow easing back to 300lb/engine/hr.

There was an absolute lack of vibration in the test aircraft.

Controls were delicate and firm, with positive and smooth responses.

At 30 DME we were at FL 210. Indicated airspeed was 190kts, OAT at -24C. Revs were at 98 per cent, fuel flow back to 220lb/engine/hr, and ITT steady at 800C. The deck angle was about five degrees as we calculated TAS at 266kts – about 307 miles an hour.

The Jetprop Commander 840 really becomes fuel efficient above FL 230, according to John Burns; as it was, at FL 200 we were burning up 240lb/engine/hr in exchange for an indicated airspeed of 190kts, 98 per cent revs and ITT of 800C. TAS in this case was 263kts/302mph.

All too soon we were inbound, 49.7 miles on the DME, with 185kts showing. Our engine and fuel flow readings had been identical for some time.

Other readouts on the descent included let-down from 43 DME to 7000ft, ITT coming back to 600C, revs to 96 per cent and fuel flow plummeting to 150Ib/hr/engine.

Sydney asked for a further descent to 5000ft. Gear was dropped to show the ruggedness of this massive undercard, at 175 indicated with negligible pitch change.

A further demonstration of the undercarriage toughness came when Sydney requested a speed increase to 190 for a short period to facilitate slot-in. With Vlo/Vle of 198, this was no sooner asked for than complied with … The minimum approach speed in the 840 is carded at 95 IAS.

It was in this phase that the winglet benefits began showing themselves. Precise control was available when needed, right down to slight flare and touch. Moderate reverse was used and, together with· moderate braking, the evaluation aircraft turned off the main runway in much less than the booked 1331ft listed for landing distance with reverse props.

Working back on performance conditions, a Jetprop Commander crew and passengers could expect a long-range cruise range at 240kts, 31,000tt, of 1740nm.

A high-speed cruise would work out to 267kts, 1708nm at FL 310, using full fuel with 45 minutes reserve.

For the book, manual figures on the 840 include:

lnitial roc, two engines, 2824fpm. Single-engine initial roc 1003fpm.

With both motors operative, the time to climb to 10,000ft is given as 3.8 minutes, with 9.5 minutes given for the FL 200 mark.

Rockwell gives a unique and typical example of the 840’s capabilities by citing a mission distance of 1396nm with seven passengers and baggage (1400lb) and fuel to full gross.

In this configuration, a cruise height of 31,000ft would return figures of time to climb of 23 minutes, cruise speed of 267kts, total time en route of 5.4 hours, and 0.654nm covered for every pound of fuel burnt off.

If that isn’t cost-effective, AADR would like to hear from any turboprop corporate twin doing better …

We liked the Rockwell Jetprop Commander 840 for its honesty and response, precise reactions to control input, its inherited rugged structure and lack of obvious vices.

The lineage is strong, brave and well-suited to Australian conditions. To own, operate or fly one of the Commander Series is perhaps a benchmark of classic taste. Statistics prove the point when it comes to balancing the cost versus utilisation and value permission at the end of a financial year.

Civil Flying Services Pty Ltd knows they have a winner on their hands. The sole criterion for the sustained success of this brilliant turboprop series will undoubtedly be the supply factor.