Too easy to makes greasers? Questions on the ground effect

[Chock 17,769]

It would seem so :wink:

 

 

Joking aside, I'd contend that if it's relatively easy to pull off a greaser, then it probably indicates PMDG got a lot of things right, as it shouldn't be difficult to get the thing down in one piece so long as you're on the numbers on your approach. After all, companies such as Boeing don't design aircraft such as the 747 to deliberately be hard to land, otherwise none of us would get on the things!

 

Not forgetting of course that one of the difficulties with creating something like a 747 for a desktop flight simulator lies in the fact that there's only so much you can do to simulate actually sitting in the real thing, so any notion of whether ground effect 'feels right', or anything else that is a bit 'seat of the pants', is going to be somewhat subjective when we've not got the luxury of a full motion platform, realistic views out of the side windows etc. All a company such as PMDG can do, is try to get the numbers right, because when a real 747 touches down and you're sat in that left seat (or the right seat), the reality is that you're the best part of fifty feet off the deck when those main wheels touch, not to mention sat at an angle looking down over that nose, and doing about 130 miles per hour. In that situation, as with landing any aeroplane for real, in addition to referencing the instruments, you're using a certain amount of 'feel' from your numerous senses to ensure you get it right; peripheral vision to help you keep it level, judging the flare off the ground rush, and so on, plus your experience of course.

[skelsey 765]

 

 

when a real 747 touches down and you're sat in that left seat (or the right seat), the reality is that you're the best part of fifty feet off the deck when those main wheels touch, not to mention sat at an angle looking down over that nose, and doing about 130 miles per hour.

 

Indeed -- I was chatting to a friend who is a former 747-400 Training Captain recently and he mentioned how odd many pilot find it when they first take off in the Jumbo because, of course, as the pilot when you pull back you go up rather a long way -- but it is possible to end up with your backside some 70-100ft in the air, with the main wheels still on the deck.

[Werner747 107]

IXEG has tweaked the xplane ground effect model so it should be pretty accurate.

 

 

you can see that when i flare to the correct attitude (5°), the vertical speed is cut rapidly but then i need to hold some back pressure to try maintainning that attitude which is not the case in the B747 in my opinion, currently the B747 behaves the same but without the need to hold some back pressure (in order to maintain that pitch attitude).

 

So i  want to know form PMDG devs if they have modelled that negative torque or not and if not if they plan to do so.

 

The 747 is NOT a 737.   The huge wing surface means that the aircraft handles vastly differently to the 737 when entering ground effect.   There is a huge cushion of air as it settles onto it-  you cannot compare ground effect of the much smaller 737 wing to that of the 747, that is comparing apples to oranges.

 

Have a look at the voluminous amount of vids on the internet about 747's landing - they all hover in ground effect for quite a bit of time before settling down.   Only in rather nasty whether, bad turbulence or some windshear will you notice a bit of a bump, or unless the pilot really gets it wrong.   I have read many posts about pilots commenting on this very aspect.

 

Regards

[Chock 17,769]

Indeed -- I was chatting to a friend who is a former 747-400 Training Captain recently and he mentioned how odd many pilot find it when they first take off in the Jumbo because, of course, as the pilot when you pull back you go up rather a long way -- but it is possible to end up with your backside some 70-100ft in the air, with the main wheels still on the deck.

 

Of course the reverse of that is when someone used to flying a 747 does it the other way around. There used to be a guy who flew with me at Camphill in the UK (a notoriously tricky glider airfield in Derbyshire with lots of windshear). He was a 747 pilot, for BA I think, and you could always tell if it was his glider coming in for a landing, because he'd be the one coming in at 95 knots who'd commence flaring whilst still 75 feet of the ground. Good job those things don't start giving you some pre-stall warning buffet until you're down to about 40 knots, cos you can't hit TOGA and go around in a glider lol.

[cmbaviator 5]

The 747 is NOT a 737.   The huge wing surface means that the aircraft handles vastly differently to the 737 when entering ground effect.   There is a huge cushion of air as it settles onto it-  you cannot compare ground effect of the much smaller 737 wing to that of the 747, that is comparing apples to oranges.

 

Have a look at the voluminous amount of vids on the internet about 747's landing - they all hover in ground effect for quite a bit of time before settling down.   Only in rather nasty whether, bad turbulence or some windshear will you notice a bit of a bump, or unless the pilot really gets it wrong.   I have read many posts about pilots commenting on this very aspect.

 

Regards

I know that a b737 is different compared to a b747 but the ground wffect physic is the same gor any aircraft. Therefore we should feel a pitching down moment on the b747. The video i posted is to only show that the ixeg had the negative putching moment and not te B747 ( maybe ?)

[downscc 1,327]

 

 

Therefore we should feel a pitching down moment on the b747.

 

You are ignoring many good observations made by others. I think you are a little too much invested in what you think should happen.

[thibodba57 462]

I know that a b737 is different compared to a b747 but the ground wffect physic is the same gor any aircraft. Therefore we should feel a pitching down moment on the b747. The video i posted is to only show that the ixeg had the negative putching moment and not te B747 ( maybe ?)

 

I don't think I've ever felt a pitching down moment from the 74...in fact if anything I've had to force the nose down once your get in ground affect.  Honestly the 74 is a lot easier than those stubby wing 73s and MD-80s.

[SledheadAK 21]

I don't think I've ever felt a pitching down moment from the 74...in fact if anything I've had to force the nose down once your get in ground affect.  Honestly the 74 is a lot easier than those stubby wing 73s and MD-80s.

 

Indeed, I've got quite a few hours in a Level-D 744 sim thanks to come airline connections and I never felt that it wanted to pitch down...  forcing the nose down was always a common occurrence. 

[scottsware 69]

The 747 is insanely easy to grease on. I flew the 737 for over 8500 hours and recently left the 320 after 3300 hours. The 737 (300 and 500) were fairly predictable. The 320, I could make a number of smooth landings then bam! The 747 landing pretty mechanically, I listen to the radio altimeter call outs. At 50' start pulling the power off, at 30' start flaring, but not a whole lot, at 10' feet, hold the site picture, which requires a tad bit of back pressure. What I noticed in the sim was you knew you touched down when you heard the spear brake moving back. It's has a loudish servo. I've done 8 landing so far in real life. It was just like the sim. 7 greasers and one so-so. The so-so was my fault. I landed flaps 30 instead of the normal 25, it was windy and the runway was SFO 19L. All a bit non standard. I fixated on the aiming spot and didn't change my focus down the runway in the flare.

 

What I'm trying to say is this simulation is pretty realistic. I think real life is a bit easier to grease it on.

[77west 139]

So far all of my landings have been pretty good apart from one where I bounced it (my own fault). I have never flow a 747 for real, but the ground effect does seem to be what I would expect, given how ground effect works.

[cmbaviator 5]

The 747 is insanely easy to grease on. I flew the 737 for over 8500 hours and recently left the 320 after 3300 hours. The 737 (300 and 500) were fairly predictable. The 320, I could make a number of smooth landings then bam! The 747 landing pretty mechanically, I listen to the radio altimeter call outs. At 50' start pulling the power off, at 30' start flaring, but not a whole lot, at 10' feet, hold the site picture, which requires a tad bit of back pressure. What I noticed in the sim was you knew you touched down when you heard the spear brake moving back. It's has a loudish servo. I've done 8 landing so far in real life. It was just like the sim. 7 greasers and one so-so. The so-so was my fault. I landed flaps 30 instead of the normal 25, it was windy and the runway was SFO 19L. All a bit non standard. I fixated on the aiming spot and didn't change my focus down the runway in the flare.

What I'm trying to say is this simulation is pretty realistic. I think real life is a bit easier to grease it on.

Nice to have an input from a b747 pilot.

 

I was landed with flaps 30, i thought it was the standard landing flaps lol.

Whats the target pitch to flare at with flaps 25 and 30 ?

 

Im just surprised on how small input you need to give in order to land

 

https://youtu.be/50rIwXiS3ck

 

 

Much harder landing : https://youtu.be/iBXwXLwGd9U

[Copper. 78]

 

 

 

 

 

 

This one might've been a "greaser" but looks like its a fraction off scraping along on its behind. Don't shoot for greasers, aim for the aiming point, let down in the TDZ. it's a very simple concept, landing. That pitch angle has to be around the 6 to 8 deg NU region.

[skelsey 765]

 

 

I was landed with flaps 30, i thought it was the standard landing flaps lol.
Whats the target pitch to flare at with flaps 25 and 30 ?

 

Did you see my reply to your earlier topic about flaring? http://www.avsim.com/topic/503457-flaring-techniques/?p=3565122

 

25 and 30 can both be used. Some airlines prefer 25 as it's a bit easier on the flaps.

 

30 in LVPs though.

 

 

Im just surprised on how small input you need to give in order to land

 

Most people I've spoken to with 747 experience highlight how little input you need in general. It's not like the 737 where you often see people yanking the controls around all over the place -- if you do that in the Jumbo you will likely end up in a PIO.

[77west 139]

 

 

25 and 30 can both be used. Some airlines prefer 25 as it's a bit easier on the flaps.

I always use F25 where possible but in the -F, where you are generally closer to MLW, this is less likely, unless on a long runway.

 

 

 

It's not like the 737 where you often see people yanking the controls around all over the place -- if you do that in the Jumbo you will likely end up in a PIO.

Agreed, ironically the 777 almost seems more difficult then the 744

[Chock 17,769]

I fixated on the aiming spot and didn't change my focus down the runway in the flare.

 

 

That's the guaranteed way to end up slamming it on in real life, when you suddenly snap out of being hypnotised by the aim point and think: 'oh s***!' then haul back on the stick a second too late. Been there done that, as I suspect most pilots have at some point. That's when you end up doing the 'walkaround of shame' checking to see if you broke anything off the poor aeroplane after you've unstrapped and got out of the thing, usually whilst rubbing your lower back lol.