Basic questions about flying jets

[oneleg]

On 1/25/2024 at 1:20 PM, PhrogPhlyer said:

Basically, a spoiler exists to to just that "spoil" the airflow, which means less lift.

In flight one wants lift, to stay on the ground, get rid of lift.

Therefore, most aircraft that have spoilers do not allow them to be activated in flight.

Excellent and clear explanation. Thank you. It makes sense.

 

But do you mean not mechanically allowed, or not allowed because of regulation and against best practice?  For what it's worth, I am able to use spoilers in flight when I'm putzing around a traffic pattern in a study-level biz jet, the Learjet 25 by Extreme Protoypes. 

A separate question: can I use reverse thrust in flight in real life?  Also, does pushing the throttle while reverse thrust has been activated enhance reverse thrust?

[jgf]

2 hours ago, oneleg said:

does pushing the throttle while reverse thrust has been activated enhance reverse thrust?

 

No.  Moving the throttles past "minimum" setting activates reverse thrust, moving them away from that position is returning to normal thrust.

 

True spoilers are rarely used in flight;  they are typically only on the upper surface of the wing to disrupt the airflow there, in doing this they also act as small ailerons, providing a downforce on both wings simultaneously (I don't know if FS models this, it is quite lenient in what you can do while flying;  I often activate spoilers on approach to bleed off speed).   Some aircraft have air brakes, these are like spoilers but on upper and lower surface of the wings (or on the sides of the rear fuselage), and extend/retract very quickly, adding immense drag to the airframe with subsequent rapid loss of speed.

 

 

[michaelkalinowsk]

Spoiler panels on the upper wing surface mostly have a tripple function. In-flight  they support flying turns. So the go up on the wing going down (where the aileron is going up) to induce a positve turning momnt. The second purpose is to increase drag in order to increase descent rate without (exceeding speed limits or speed instructed by ATC. Then the spoiler panels go up on both wings and are controlled by the speed brake lever in the center pedestal. The third function is on ground after touch down when the spoilers go fully up in order to spoil the lift and increase drag to reduce the stop distance. Ground spoiler operation is armed by the pilots before landing and after wheel spin up they are commanded to raise. If the pilots for whatever reason initiate a go-around after touch down with ground spoiler already deployer, the spoilers retract automatically when the go-around thrust is commanded for the engines.

 

Michael

[oneleg]

10 hours ago, jgf said:

 

No.  Moving the throttles past "minimum" setting activates reverse thrust, moving them away from that position is returning to normal thrust.

 

True spoilers are rarely used in flight;  they are typically only on the upper surface of the wing to disrupt the airflow there, in doing this they also act as small ailerons, providing a downforce on both wings simultaneously (I don't know if FS models this, it is quite lenient in what you can do while flying;  I often activate spoilers on approach to bleed off speed).   Some aircraft have air brakes, these are like spoilers but on upper and lower surface of the wings (or on the sides of the rear fuselage), and extend/retract very quickly, adding immense drag to the airframe with subsequent rapid loss of speed.

 

 

Yes, I know moving throttles past "minimum" activates reverse thrust (holding F2 in P3D) and returning them to their original position (F1) deactivates reverse thrust and creates normal thrust. But in Xtreme Prototypes Learjet 25, the throttle can apparently be moved forward while reverse thrust is still active and reverse thrust still appears to be active after moving the throttle on the joystick forward.  I'm wondering if moving the throttle forward in that aircraft model increases the force of the reverse thrust.

 

Are there business jets with air brakes?  I know in DCS, the A-10C has them. 

[Mike80]

12 minutes ago, oneleg said:

-----Are there business jets with air brakes?  I know in DCS, the A-10C has them. ---

Sometimes there is understandable confusiion among terms "spoilers", "air brakes" , "speed brakes" and spoilers. 

 

True spoilers are for dumping lift on the runway to get the most weight on wheels for braking and aero deceleartion. Some designs have integrated modes with several individual panels wherein certain ones can be operated in flight to a certain degree for a speed brake mode.  Brits seem to use the term air brake for what yanks call speed brakes or in the military "the boards".

 

Military tactical jets typically have large speed brakes for use in dive bombing in steep runs as well as rapid deceleration when needed. Every military tactical jet I flew had no airspeed limit on the use of speed brakes (i.e, A-4, A-6, EA-6B A-3, F-4, T-38, T-2, F9F-8 etc). However these were fuselage mounted and did nort exert any extraneous force on the wings

[PhrogPhlyer]

56 minutes ago, Mike80 said:

Sometimes there is understandable confusiion among terms "spoilers", "air brakes" , "speed brakes" and spoilers. 

This might help oneleg...

https://skybrary.aero/articles/spoilers-and-speedbrakes

 

[PhrogPhlyer]

5 hours ago, Mike80 said:

Every military tactical jet I flew had no airspeed limit on the use of speed brakes

Not a jet, but with the T-28C the only speed brake limitation we had (more of a note) was that use of the speed brake above 250kt would generate a strong pitch change but controllable with forward stick.

 

[PhrogPhlyer]

1 hour ago, Mike80 said:

F9F

OK, I am impressed!

Great aircraft.

[Mike80]

3 hours ago, PhrogPhlyer said:

OK, I am impressed!

Great aircraft.

It was indestructible. I flew both dual and single seat models as a student at Kingsville, 2- seaters as an instructor at Beeville.

 

Most over-engineered thing you could imagine; triple redundant everything. It was th Navy's first swept wing carrier aircraft and they hyperventilated about everything that might go wrong, but in the end it was pretty damned good.

[avallillo]

Just about all jets have devices on the upper wings that function as both spoilers (on the ground) and speed brakes (in the air).  Every jet I ever flew except the C-5 was equipped this way (C-141, B-707, B-727, B757, B-767, A-300).  On the C-5, the devices were only for ground use as spoilers.  On that airplane, if you wanted to decelerate in the air, or increase rate of descent, you could use reverse thrust on the inboard engines.  The DC-8 also had in-flight thrust reverse; I never flew it, so I don't know if the spoilers could be used in flight as speed brakes. 

 

One of the more interesting "speed brake" set ups was on the DC-7, the 4 engine propliner.  On that airplane, "speed brakes" was the extension of the main landing gear only, with the nosewheel still in the well.  Since speed brakes are merely drag producing devices, that setup worked well to keep from shock cooling the temperamental tubo compound engines.

[mrzippy]

@Mike80 Did you ever fly Banshees?  The skipper of Saratoga (CVA60) Capt. Warren H. O'Neil was in a Banshee squadron in the early 50's.

[oneleg]

5 hours ago, PhrogPhlyer said:

This might help oneleg...

https://skybrary.aero/articles/spoilers-and-speedbrakes

 

It sure did help. Excellent info on spoilers and the like. Thank you.

[Mike80]

10 hours ago, mrzippy said:

@Mike80 Did you ever fly Banshees?  The skipper of Saratoga (CVA60) Capt. Warren H. O'Neil was in a Banshee squadron in the early 50's.

No, they were out of service by that time, being replaced by F-8s and F-4s. However many mid and senior grade officers (O-4 and O-5) in the squadrons in our Air Wing had flown them in Korea.

 

I used to pick their brains about carrier ops in those days. Some of them had flown Demons, several Skyraider drivers as well (John McCain included).

[PhrogPhlyer]

1 hour ago, Mike80 said:

Korea

The forgotten war, especially for Naval Aviation (Navy brown shoes, and Marines).

The transitional period of aircraft design and capabilities.

[mrzippy]

20 minutes ago, PhrogPhlyer said:

The forgotten war, especially for Naval Aviation (Navy brown shoes, and Marines).

The transitional period of aircraft design and capabilities.

Thanks, Phrog!  Never really heard that term used, even though I was an Aviation Electronics Tech 2nd Class petty officer.  I do remember the term "Black Shoe" referencing non aviation ship's personnel.

The term “brown shoe” dates to 1913, when Naval aviators adopted brown leather shoes to hide an airfield's dust, while sailors on ships with plenty of tar and coal wore black shoes.

 

I see you lurking there Mike! 

[oneleg]

Different topic but still a question about flying jets (and flying in general).

How does one determine and differentiate between ground and flight idle on the tachometer, and how are those two types of idling different in props?  Is idling the same as leaning the engine?