AJ From Australia, joined Nov 1999, 2285 posts, RR: 24 Reply 1, posted (3 years 6 months 3 weeks 5 days 4 hours ago) and read 1787 times:
I believe what you are referring to are the vortex generators, there to stimulate airflow over the high speed aileron. Do you mean the objects behind the inboard engine pylon?
Miamiair From , joined Dec 1969, posts, RR: Reply 2, posted (3 years 6 months 3 weeks 5 days 3 hours ago) and read 1770 times:
The black and white at the bottom of the picture is the emergency walkway to direct the occupants aft. It is a coating that has something like sand in it to give traction.
Prebennorholm From Denmark, joined Mar 2000, 4814 posts, RR: 50 Reply 4, posted (3 years 6 months 3 weeks 4 days 20 hours ago) and read 1622 times:
It's a string of vortex generators. They are only in front of the high speed ailerons which are placed behind engines #2 and 3. They are not often found on modern airliners.
The 707 has a wing profile which is pretty much curved on the upper surface. It was needed to generate enough lift for take-off and landing on older planes which do not have modern leading edge slats.
That curvature accelerates the airflow more than the more flat upper surface on modern airliners.
If a 707 should be "overspeeding", say, accidentally hit Mach 0.90 or something like that, then the airflow would become supersonic on the upper surface of the wing, especially if it at the same time was flying at high angle of attach, say, recovering from a slight dive at high altitude. A sonic chock front would be created on the upper surface. That would make the ailerons ineffective.
The vortex generators have very little drag at subsonic airflow. But at supersonic airflow they generate very high drag. That slows the airflow so the airflow remains subsonic at slight overspeeding, and the ailerons remain effective at a higher Mach number than without the vortex generators.
In short: A precaution to maintain aileron effectiveness at slight overspeeding.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
411A From United States, joined Nov 2001, 1538 posts, RR: 5 Reply 7, posted (3 years 6 months 3 weeks 4 days 16 hours ago) and read 1533 times:
If you look closely at the underside of the horizontal stabilizer on some (but not all) 707's, you will also see a row of vortex generators, installed for the same purpose as previously described.
Also, the 'high speed' aileron referred to is actually called the ...inboard aileron.
DC8Friendship From United States, joined Apr 2005, 186 posts, RR: 2 Reply 8, posted (3 years 6 months 3 weeks 4 days 16 hours ago) and read 1520 times:
Actually found on quite a few modern airliners (the faster ones).
Quoting Prebennorholm (Reply 4): It was needed to generate enough lift for take-off and landing on older planes which do not have modern leading edge slats.
707's Did have leading edge devices, variable camber flaps, to increase lift.
411A From United States, joined Nov 2001, 1538 posts, RR: 5 Reply 9, posted (3 years 6 months 3 weeks 4 days 3 hours ago) and read 1428 times:
The very early models definitely did not, and a few others (138/138B, for example) only had one section.
Full span leading edge devices arrived with the -320B models (except a few -320 non-fan models specifically made for SAA).
Miamiair From , joined Dec 1969, posts, RR: Reply 10, posted (3 years 6 months 3 weeks 4 days 3 hours ago) and read 1414 times:
707's did NOT have variable camber devices, such as those on the 747. The 707 has leading edge slats and Kruger flaps inboard of the inboard engines. The leading edge slats on the 707 are not like those found on the rest of the Boeing/Lockheed/Douglas jets. The 707 slats are hinged; rotate downward and forward to extend and have a bull-nose fairing that extends by means of a bell crank linkage.
AeroWeanie From United States, joined exactly 4 years ago today! , 1511 posts, RR: 38 Reply 12, posted (3 years 6 months 3 weeks 3 days 1 hour ago) and read 1282 times:
Quoting Miamiair (Reply 10): 707's did NOT have variable camber devices, such as those on the 747. The 707 has leading edge slats and Kruger flaps inboard of the inboard engines. The leading edge slats on the 707 are not like those found on the rest of the Boeing/Lockheed/Douglas jets. The 707 slats are hinged; rotate downward and forward to extend and have a bull-nose fairing that extends by means of a bell crank linkage.
Only the 747 has variable camber Krueger flaps on the leading edge (actually, the 787 is rumored to have variable camber Kruegers too).
The 707 doesn't have slats, only fixed camber Kruegers.
Quoting Prebennorholm (Reply 4): If a 707 should be "overspeeding", say, accidentally hit Mach 0.90 or something like that
The Mmo of the 707-120 is .90, so it wouldn't be overspeeding to hit .90. The 707-138 Mmo is .91! The 707-320 Mmo is .887. Additionally, they are certified out to Mdive, which is .95 on the 707-320.
VGs are commonly added to airliner wings to tailor stall characteristics (767, etc.) or to counter aileron buzz.
OldAeroGuy From United States, joined Dec 2004, 2549 posts, RR: 50 Reply 13, posted (3 years 6 months 3 weeks 2 days 23 hours ago) and read 1264 times:
Quoting Prebennorholm (Reply 4): It's a string of vortex generators. They are only in front of the high speed ailerons which are placed behind engines #2 and 3. They are not often found on modern airliners.
You'll find VG's on every Boeing airliner except the 747.
Quoting AeroWeanie (Reply 12): VGs are commonly added to airliner wings to tailor stall characteristics (767, etc.) or to counter aileron buzz
Most VG installations are added to improve high speed pitch characteristics. A giveaway is that they are located at about the front spar chordwise. This is much too far aft to help with stall handling.
The vortillons (a VG by another name) on a 737NG are located on the slat leading edge. This a spot more likely to influence stall characteristics.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Miamiair From , joined Dec 1969, posts, RR: Reply 14, posted (3 years 6 months 3 weeks 2 days 23 hours ago) and read 1263 times:
411A:
The 707 does have slats. Outboard of the inboard engines are all slats. The nomenclature in the Illustrated parts Catalog (IPC) is :SLATS. I will agree that they do not look like the slats we see the extend forward on tracks like on the MD-80, but 707 does have slats. If you want email me and I will send you a page.
Matt72033 From United Kingdom (England), joined May 2005, 1617 posts, RR: 4 Reply 15, posted (3 years 6 months 3 weeks 2 days 23 hours ago) and read 1253 times:
I thought vortex generators where to re-energize the boundary layer? Helping it to adhere to the surface of the wing at high AoA?
AeroWeanie From United States, joined exactly 4 years ago today! , 1511 posts, RR: 38 Reply 16, posted (3 years 6 months 3 weeks 2 days 23 hours ago) and read 1254 times:
Quoting OldAeroGuy (Reply 13): The vortillons (a VG by another name) on a 737NG are located on the slat leading edge. This a spot more likely to influence stall characteristics.
Are these only on 737NGs with winglets are they on all 737NGs? In some cases, I think I can see them on non-wingletted aircraft, in other cases, I don't think they are there.
OldAeroGuy From United States, joined Dec 2004, 2549 posts, RR: 50 Reply 17, posted (3 years 6 months 3 weeks 2 days 22 hours ago) and read 1250 times:
AeroWeanie,
On all 737NGs, with or without winglets.
Quoting Matt72033 (Reply 15): I thought vortex generators where to re-energize the boundary layer? Helping it to adhere to the surface of the wing at high AoA?
Nope, you're correct. At Vmo/Vd though, you don't need to be very high in AoA to need more boundary layer energy.
Quoting AeroWeanie (Reply 16): They might be called slats in the IPC, but they are actually Krueger flaps
I agree.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Amtrosie From United States, joined Jan 2005, 274 posts, RR: 0 Reply 18, posted (3 years 6 months 3 weeks 2 days 18 hours ago) and read 1211 times:
Krueger flaps and slats are both leading edge devices. period. There are differences, and they are referred to separately in the IPC for a very specific reason. Never in all my years of working in the Boeing manuals (any other one for that matter), have they referred to one thing and meant another. For those of us who have to be specific about what we are referring to and working on, for the benefit of the FAA and other such entities, to say one thing and mean another is mind boggling!!
Miamiair From , joined Dec 1969, posts, RR: Reply 19, posted (3 years 6 months 3 weeks 2 days 17 hours ago) and read 1195 times:
IMHO,
I can understand why people are baffled by the "slats" on the 707. As I learned aviation terminology as a kid, slats are what a DC-9 had. Those are the slats that extended downward on tracks, but did not tuck under the leading edge as on the 707.
When I worked on the 707, I learned that the leading edge devices are known as slats. The slats on the 707 are magnesium castings that have a fairing and attach arms on them. They are identical in operation to the Kruger Flaps, but have a different nomenclature and a different structural composition.
But, according to Boeing, these things on the 707 leading edge outboard of the inboard engines are ...slats.
Scarebus03 From Ireland, joined Apr 2005, 165 posts, RR: 1 Reply 20, posted (3 years 6 months 3 weeks 16 hours ago) and read 1044 times:
The main difference between slats and flaps as I understand it is that a leading edge slat creates a slot for high energy air to energise the boundary layer at low speeds and a kruger flap does not . So do Kruger flaps create a slot? Because a leading edge slat definitely does but I do not think that a kruger leading edge flap does hence the difference in nomenclature. The kruger is a flap and not a slat. Trailing edge flaps on big airliners create slots but on smaller aircraft normally not. Krugers only change the camber and do not create slots.
AeroWeanie From United States, joined exactly 4 years ago today! , 1511 posts, RR: 38 Reply 21, posted (3 years 6 months 3 weeks 15 hours ago) and read 1042 times:
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