777X set for January 23rd first flight

[VH DSJ]

Originally Posted by 568

It is standard practice on maiden flights.

I gathered that, but I'm asking why?

[Dave Therhino]

Originally Posted by VH DSJ

I gathered that, but I'm asking why?

I'm speculating, but I think it's simply risk reduction - one less thing to worry about going wrong on the first flight. The landing gear obviously is fully ready for the flight, but they are typically verifying lower speed characteristics on the first flight, so leaving the gear down doesn't limit them much. You can bet if an engine failure occurred on takeoff they would have raised the gear.

[WingNut60]

Originally Posted by Dave Therhino

I'm speculating, but I think it's simply risk reduction - one less thing to worry about going wrong on the first flight. The landing gear obviously is fully ready for the flight, but they are typically verifying lower speed characteristics on the first flight, so leaving the gear down doesn't limit them much. You can bet if an engine failure occurred on takeoff they would have raised the gear.

But five hours with the gear down ?????????????

[SamYeager]

Originally Posted by WingNut60

But five hours with the gear down ?????????????

Just don't tell Greta about the effect on fuel consumption.

[733driver]

I have often wondered the same thing. Why keep the gear down throughout may of these first flights? It doesn't seam to me like a landing gear would be likely to malfunction and if it did there'd be contingency procedures. There are much bigger risks associated with a first flight that are happily accepted but the gear. I really don't understand. But I'm not a test pilot and I#d be happy to learn.

[DaveReidUK]

A350 first flight 2013:



Gear goes up at about 2:06

[Auxtank]

Boeing test flight evaluation and procedural testing is different to Airbus.

A load of stability, handling and system evaluations are done prior to retracting the landing gear on Boeings. Has been that way for a long time.
Airbus must do same tests but in a different order regarding landing gear position.

[Less Hair]

Has the gear mechanism been changed compared to the 777-300ER? The wing is new so must be the wing box and gear bay.

[Simo Lallukka]

During final taxing or towing the plane windshield wipers did not look ok. Other wiper worked half way and other wiper was not working. It was shown in Finnish tv-news clip, they did not comment this.

[b1lanc]

Originally Posted by Dave Therhino

I'm speculating, but I think it's simply risk reduction - one less thing to worry about going wrong on the first flight. The landing gear obviously is fully ready for the flight, but they are typically verifying lower speed characteristics on the first flight, so leaving the gear down doesn't limit them much. You can bet if an engine failure occurred on takeoff they would have raised the gear.

That's exactly the protocol that a Boeing test-pilot stated in a televised interview just after touchdown. He also added the embarrasment factor - first flight, a lot of press, what if they raise the gear and then - use your imagination on how far that set of unknowns could set the program back and the resultant black eye for B when they already have their quota of black-eye boxes checked.

[DaveReidUK]

Originally Posted by Less Hair

Has the gear mechanism been changed compared to the 777-300ER? The wing is new so must be the wing box and gear bay.

AFAIK, the gear on the 777-9 is substantially the same as the -300ER's (same mfr), though the new wing has resulted in the track being 6" less.

[Less Hair]

Did they keep the gear down for the entire 787 first flight back then?

[WB627]

Does the 777X rely on "grandfather rights" for certification, in the same way the 737 Max did?

[DaveReidUK]

Originally Posted by Less Hair

Did they keep the gear down for the entire 787 first flight back then?

See post #58.

Originally Posted by WB627

Does the 777X rely on "grandfather rights" for certification, in the same way the 737 Max did?

Yes.

[Pilot DAR]

rely on "grandfather rights" for certification

It's not "grandfather rights". The airplane presented for certification to the FAA will be presented one of three ways: A brand new design, to the latest design requirements, A derivative of a type for which the manufacturer holds a type certificate, approved to the original certification basis (very unlikely for an airliner), Or, A derivative of a type for which the manufacturer holds a type certificate, approved to an updated certification basis - most likely scenario. The applicant and the FAA will agree with a certification basis under the "changed product rule (CPR)" guidelines. It is certain that when CPR is exercised correctly, the most applicable and practical more recent design requirements will be applied to the derivative design. It would not always be possible to apply the latest design requirements to a derivative of an older design, so the FAA realizes the need for discussion and compromise. The CPR determination will be documented for future reference.

It will not be a case of "the oldest" (grandfather), or the newest (may as well be a whole new design, for the work involved), it will be a well thought out compromise. Recent history with the 737 MAX and MCAS would suggest that a part of the CPR process was not correctly applied for that change. I'm confident that someone is reviewing that. In the mean time, I have to hope that the need for objective application of the CPR process will be fresh in the FAA's mind these days!

[Auxtank]

Originally Posted by Simo Lallukka

During final taxing or towing the plane windshield wipers did not look ok. Other wiper worked half way and other wiper was not working. It was shown in Finnish tv-news clip, they did not comment this.

Windshield wipers on the 777 are controlled independently of one another and have their own switches on each side of the overhead panel.
Settings are; Off - Intermittent - Low - High. The wiper arms have a relatively low radius of movement (compared to your car's windscreen wipers) and don't traverse the entire screen.

[tdracer]

I wonder if the 'gear down' dates back to the 767 first flight experience - when they retracted the gear on the 767 first flight the nose gear sheared a hydraulic line. They quickly put the gear back down before they lost that hydraulic system, but they flew the balance of the first flight with one hydraulic system inop (apparently they'd identified the nose gear issue prior to first flight, and installed a re-designed part - but the paperwork hadn't caught up and the new bracket was identified as a non-conformance and replaced with the original part prior to flight - oops ).

To elaborate a bit on what Pilot DAR posted - CPR basically says that anything that is being changed relative to the original cert basis needs to meet the latest regulation. There is precious little common between the original 777 and the 777X (new wing, engines, most avionics, even the fuselage structure has been changed) so it may not be a complete new cert to the latest regs, but it's close.

[Auxtank]

Good point td,
I think Boeing are rather conservative when it comes to First Flight Test Procedures.
What's worked in the past - works now - will work... sort of mentality.

I know Airbus do it differently - in fact they see it as a matter of principle (perhaps as a re-asurrance to on-looking customers and pax) that the gear goes up in a timely fashion - but old procedures, old and tried and tested lists and actions to get a new frame flying good; are the progenitors of Redundancy - when you've done the procedure so many times...

Airbus' early gear up on first flight wasn't necessarily a two-finger salute to Boeing - doesn't mean the aircraft is any safer, any better...
Just means the boffins at the drawing boards have reckoned efficiency is better on initial tests with gear retracted and worth the risk...

Neither's right, neither's wrong. Horses for courses.

[Longtimer]

Originally Posted by WingNut60

But five hours with the gear down ?????????????

Looking at the Boeing flight tracker site, the entire mission was done at relatively low speeds. Mostly under 350KPH.

[Auxtank]

Originally Posted by Longtimer

Looking at the Boeing flight tracker site, the entire mission was done at relatively low speeds. Mostly under 350KPH.

With the gear down - it would be...
Under 270 KIAS actually...(and probably well under that..)