I remember reading somewhere that on some jetliners it is not recommended to lower gear and flaps at the same time as this places too much demand on the hydraulic system or for some other reason. The Boeing 707? For pilots and those informed, what is standard operating procedure for your aircraft when it comes to lowering flaps and landing gear?

I watched a cockpit video of a 747 during approach and landing and the pilot flying the aircraft called out "Gear down flaps 20" so I am guessing it is okay to lower flaps and gear simultaneously on the 747.

convair880mfan wrote:

I remember reading somewhere that on some jetliners it is not recommended to lower gear and flaps at the same time as this places too much demand on the hydraulic system or for some other reason.

Sorry, can’t really contribute to the topic, but I think you read this a few months ago in this thread:

viewtopic.php?f=5&t=1459639

Flow2706 wrote:

It is also considered good airmanship not to move the flaps and the gear at the same time to avoid peak loads on the green hydraulic system (this is also not a limitation/procedure, but is considered good airmanship).

convair880mfan wrote:

I remember reading somewhere that on some jetliners it is not recommended to lower gear and flaps at the same time as this places too much demand on the hydraulic system or for some other reason. The Boeing 707? For pilots and those informed, what is standard operating procedure for your aircraft when it comes to lowering flaps and landing gear?

I watched a cockpit video of a 747 during approach and landing and the pilot flying the aircraft called out "Gear down flaps 20" so I am guessing it is okay to lower flaps and gear simultaneously on the 747.

From a bit of 737 sim time I’ve had in this is a standard call:

> at glide slope intercept: Pilot Flying calls “gear down, flaps 15”

This is because caution warning sounds if the Dunlop’s aren’t dropped when moving to flaps 15.

Saying “gear down, flaps 15”, doesn’t mean actually moving them simultaneously. For example, the gear needs to indicating green to avoid the flap warning, so there might be a slight delay on moving the flap handle.

GalaxyFlyer wrote:

Saying “gear down, flaps 15”, doesn’t mean actually moving them simultaneously. For example, the gear needs to indicating green to avoid the flap warning, so there might be a slight delay on moving the flap handle.

Fair point. But in my (limited) experience they are consecutive actions by PNF so gear is still in transit when the flap lever is moved to 15 degrees. Happy to be corrected.

Can't speak for other aircraft but for both the 747-200 and 400, 2 miles prior to the FAF or OM (or thereabouts for visuals), standard maneuver calls for 'gear down' flaps 20 (Assuming the flaps were already at 10 for maneuvering). It's done simultaneously. I don't recall any restrictions. After gear is down, then flaps 25, landing check.

RetiredWeasel wrote:

Can't speak for other aircraft but for both the 747-200 and 400, 2 miles prior to the FAF or OM (or thereabouts for visuals), standard maneuver calls for 'gear down' flaps 20 (Assuming the flaps were already at 10 for maneuvering). It's done simultaneously. I don't recall any restrictions. After gear is down, then flaps 25, landing check.

On the B747, landing gear and flaps are on systems 1&4. As I recall, inboard flaps, body gear and nose gear are on the #1 system, outboard flaps and wing gear are on the #4. Between the 2 systems there are 4 pumps…2 eng driven, 2 air driven.

The pumps are, something like, 50gpm @ 3000psi, each. Plenty of fluid and power to move everything.

convair880mfan wrote:

I remember reading somewhere that on some jetliners it is not recommended to lower gear and flaps at the same time as this places too much demand on the hydraulic system or for some other reason. The Boeing 707? For pilots and those informed, what is standard operating procedure for your aircraft when it comes to lowering flaps and landing gear?

I watched a cockpit video of a 747 during approach and landing and the pilot flying the aircraft called out "Gear down flaps 20" so I am guessing it is okay to lower flaps and gear simultaneously on the 747.

IIRC, the Gear Ext/Ret and Flaps are run by different hydraulic systems on most aircraft especially jetliners, and each engine drives it's own hydraulic pump which on twin engine jetliners #1 Engine Hydraulic Pump runs different items on it's system compared to #2 Engine Hydraulic Pump. So deploying gear and flaps are on 2 different hydraulic systems so there would never be 'too much demand.'







Then again, on some twins, there are no engine driven pumps for a hydraulic system, 767 has 2 electric pumps running the center hydraulics...



Lots of similarities and differences between different aircraft and their hydraulic systems....

CALTECH wrote:

Then again, on some twins, there are no engine driven pumps for a hydraulic system, 767 has 2 electric pumps running the center hydraulics...

Don’t forget the air-driven pump.

fr8mech wrote:

RetiredWeasel wrote:

Can't speak for other aircraft but for both the 747-200 and 400, 2 miles prior to the FAF or OM (or thereabouts for visuals), standard maneuver calls for 'gear down' flaps 20 (Assuming the flaps were already at 10 for maneuvering). It's done simultaneously. I don't recall any restrictions. After gear is down, then flaps 25, landing check.

On the B747, landing gear and flaps are on systems 1&4. As I recall, inboard flaps, body gear and nose gear are on the #1 system, outboard flaps and wing gear are on the #4. Between the 2 systems there are 4 pumps…2 eng driven, 2 air driven.

The pumps are, something like, 50gpm @ 3000psi, each. Plenty of fluid and power to move everything.

Ya the air pumps came on normally on demand (when the hyd. pressure dropped a certain amount) and the run lights would light up on the engineer's panel (the 200). This happened frequently on the 200 when making heavy use of the hydraulic systems.

At my operator, it is convention to lower gear first, wait until it has stopped transiting, then call flaps 3. However, there's no limitation on doing them together.

On the A330, slats are powered by blue + green systems, whilst flaps are powered by green + yellow systems. If you lose a system, the associated surfaces move more slowly. E.g. if you lose the yellow system, slats move at full speed and flaps slowly.

It may be different for Civilian Aircraft, but for Military jets ( i.e. the rhino) depending on the CASE of the recovery you would drop the gear and the flaps at the same time. The rhino also has only 2 Hyd systems as well, and has room to spare.


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Lowering the gear doesn’t put much demand on the hydraulic system. Once the gears unlock they free fall for the most part. Retracting them is another story.

>From a bit of 737 sim time I’ve had in this is a standard call:
> at glide slope intercept: Pilot Flying calls “gear down, flaps 15”

That doesn't sound correct for a Boeing. You want flaps 15 once you're in the terminal area and you also have a target speed. As you come up on the glideslope, at one to two dots above you want to call gear down. This gives the gear time to extend and lock down before glideslope capture...because at glideslope capture you want to call landing flaps. This procedure is for all engines operating flying an ILS. A single engine approach and landing the procedure will be different.

RalphF
http://www.GMTPilots.com

rfresh737 wrote:

>From a bit of 737 sim time I’ve had in this is a standard call:
> at glide slope intercept: Pilot Flying calls “gear down, flaps 15”

That doesn't sound correct for a Boeing. You want flaps 15 once you're in the terminal area and you also have a target speed. As you come up on the glideslope, at one to two dots above you want to call gear down. This gives the gear time to extend and lock down before glideslope capture...because at glideslope capture you want to call landing flaps. This procedure is for all engines operating flying an ILS. A single engine approach and landing the procedure will be different.

RalphF
http://www.GMTPilots.com

There used to be a video that has since been made private, but there was this one dude a few years back who took on a challenge to learn to fly the 737 in a month, and I definitely remember him calling out "Gear down, flaps 15." I'm not sure if procedures vary between airlines, but I definitely remember it.

rturner wrote:

It may be different for Civilian Aircraft, but for Military jets ( i.e. the rhino) depending on the CASE of the recovery you would drop the gear and the flaps at the same time. The rhino also has only 2 Hyd systems as well, and has room to spare.


Sent from my iPhone using Tapatalk

In UPT right now, I was about to say for both the T6 and T1 we’re doing gear and flaps at the same time.

“Check handle down, three green, flaps takeoff”

rfresh737 wrote:

>From a bit of 737 sim time I’ve had in this is a standard call:
> at glide slope intercept: Pilot Flying calls “gear down, flaps 15”

That doesn't sound correct for a Boeing. You want flaps 15 once you're in the terminal area and you also have a target speed. As you come up on the glideslope, at one to two dots above you want to call gear down. This gives the gear time to extend and lock down before glideslope capture...because at glideslope capture you want to call landing flaps. This procedure is for all engines operating flying an ILS. A single engine approach and landing the procedure will be different.

RalphF
http://www.GMTPilots.com

That is the correct procedure, at least on the 737NG. If you select flaps 15 with the gear up, you will get the landing gear warning horn, and it cant be silenced.

We usually aim for flaps 1 on downwind, flaps 5 on base and at g/s intercept it's "gear down, flaps 15". At my airline landing flaps must be set prior to 1000' AFE. For a single engine ILS we call "gear down, flaps 15" at one dot fly up. If you have the power set, and are on speed the airplane will be right about target speed at glide slope intercept.

>There used to be a video that has since been made private, but there was this one dude a few years back who took on a challenge to learn to fly the 737 in a month, and I definitely remember him calling out "Gear down, flaps 15." I'm not sure if procedures vary between airlines, but I definitely remember it.

Oh procedures vary between airlines big time. When I worked for Lockheed on the L-1011 I was amazed at how differently each airline flew the Tristar. They all had different normal, abnormal and emergency checklists. I was amazed that you could shut down an engine due to fire so many different ways!! Then I learned that the airlines did this for standardization within their fleet. Delta at that time flew the 747, DC-10 and L-1011. They wanted their procedures to be as similar as possible for their pilots who flew those 3 jets.

So while you can read the official Boeing POH on how to fly an ILS (when and where to put flaps out and gear down), the larger carriers will "do it their way" while smaller Boeing customers will just adopt the Boeing procedures as is.

RalphF
www.GMTPilots.com

rfresh737 wrote:

>From a bit of 737 sim time I’ve had in this is a standard call:
> at glide slope intercept: Pilot Flying calls “gear down, flaps 15”

That doesn't sound correct for a Boeing. You want flaps 15 once you're in the terminal area and you also have a target speed. As you come up on the glideslope, at one to two dots above you want to call gear down. This gives the gear time to extend and lock down before glideslope capture...because at glideslope capture you want to call landing flaps. This procedure is for all engines operating flying an ILS. A single engine approach and landing the procedure will be different.

RalphF
http://www.GMTPilots.com

Incorrect, you put the gear down prior to selecting flap 15 otherwise you get the horn….