Go Back  RCU Forums > RC Airplanes > RC Jets
Reload this Page >

Gear up in missed approach.

Notices
RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems

Gear up in missed approach.

Old 12-12-2016, 12:21 AM
  #1  
luge_racer
Thread Starter
 
Join Date: May 2015
Posts: 228
Received 2 Likes on 2 Posts
Default Gear up in missed approach.

I was just pondering an idea, and it could be a stupid one, so please tell me if it's terrible.

I was watching videos of full scale jets landing on YouTube (mostly F-15s) and noticed that when they need to wave off a landing they immediately bring the gear up; presumably to reduce drag while they're in a low speed, low power situation while the engines take time to spool up.

Now, I've had my fair share of waved off landings on my jets and I know it takes many seconds for the engines to spool up (and seems like an eternity); on a heavy, draggy airframe the usable power doesn't come on until late. I've never had the wherewithal to bring the gear up on a missed approach. I have to land on either a 300 ft, or 450 ft runway, so I can't just let her glide on and touch down much beyond the runway threshold.

Often times I'll have an airbrake or crow mix active when on the landing approach that automatically closes when I push past 3/4 throttle. This allows me to clean up the airframe without thinking about it when I have to call off a landing. What if I apply the same idea to landing gear: a mix that pulls the gear up only when the plane is in a landing configuration if you hit full throttle. It could be in its own landing flight condition, or simply tied to full flaps. The idea being to reduce drag in that critical wave off stage.

Has anyone else done this? Is it a terrible idea? Just throwing it out there.
Old 12-12-2016, 12:37 AM
  #2  
highhorse
My Feedback: (2)
 
highhorse's Avatar
 
Join Date: Nov 2006
Location: Memphis, TN
Posts: 2,509
Received 83 Likes on 42 Posts
Default

Yeah, it's an idea better left undone, IMO.

What if your go-around is last-instant and you make contact with the runway in spite of your best efforts? You sure don't want the h]gear retracting then. Or what about touch and goes? Same thing. Lastly, if you have gear doors that are normally closed when gear is extended and then open for retraction, then you're actually adding drag until those doors close again.

All in all, I'd just let things be and keep it simple.
Old 12-12-2016, 05:08 AM
  #3  
TonyBuilder
My Feedback: (11)
 
TonyBuilder's Avatar
 
Join Date: Mar 2010
Location: Austin , TX
Posts: 4,166
Likes: 0
Received 0 Likes on 0 Posts
Default

Why not just flip the gear switch up and go around? If your not use to this try putting your gear up on take off once you are safely rotated but before the turn.

TB
Old 12-12-2016, 07:51 AM
  #4  
bonanzadrv
My Feedback: (21)
 
Join Date: Jan 2002
Location: Joliet, IL
Posts: 274
Likes: 0
Received 0 Likes on 0 Posts
Default

In most full scale (mil fighters maybe not) you want to wait until a positive rate of climb is established before gear up.

I agree with high horse that retracting gear causes more drag than gear down does... That's why in full scale wind shear or stall recovery the configuration is left unchanged until the airplane is flying again..

I just wait until turbine spool up and the aircraft starts pitching up and then hit the gear switch...

Bill


Old 12-12-2016, 11:10 AM
  #5  
luge_racer
Thread Starter
 
Join Date: May 2015
Posts: 228
Received 2 Likes on 2 Posts
Default

I guess that my thought was automation would reduce the pilot workload in a critical situation; it could even be put on a delay so that the gear doesn't retract immediately, just in case you do bounce.

I rarely do touch and goes with my turbines, my landing strips just aren't long enough to do them comfortably. But, "touch and go" could be on its own flight condition.

I also don't currently have any aircraft where the doors would cause much issue.
Old 12-12-2016, 03:04 PM
  #6  
stevekott
 
stevekott's Avatar
 
Join Date: Nov 2006
Location: yorba linda, CA
Posts: 595
Likes: 0
Received 0 Likes on 0 Posts
Default

It's a judgement call but .... I would just as well prefer to leave the gear down.

There's always a chance they could get hung on their way back down. You will be that much closer to zero fuel flameout on a go around and not time.to try and dislodge them.

Compare to full scale our models have so much higher power to weight ratio and getting a positive rate of climb with gear down is pretty easy. I think I would retract flaps to 10 degrees, that drops a.lot of drag.

Just my two cents.
Old 12-12-2016, 04:09 PM
  #7  
causeitflies
 
causeitflies's Avatar
 
Join Date: Jan 2003
Location: EASTERN OHIO
Posts: 2,389
Likes: 0
Received 33 Likes on 27 Posts
Default

^ +1 Go from landing flap to takeoff flap.
Old 12-12-2016, 04:55 PM
  #8  
Vincent
My Feedback: (61)
 
Vincent's Avatar
 
Join Date: Dec 2001
Location: Arizona
Posts: 4,966
Received 10 Likes on 9 Posts
Default

Our models are so over powered so I don't change a thing just pedal to the metal and concentrate on setting up a new approach that will get me down safely. Vin...

Last edited by Vincent; 12-13-2016 at 06:14 AM.
Old 12-12-2016, 07:13 PM
  #9  
2walla
My Feedback: (10)
 
Join Date: Mar 2003
Location: walla walla, WA
Posts: 728
Likes: 0
Received 0 Likes on 0 Posts
Default

Just fly the plane..leave the gear alone.. most full scale have airspeed limits on the gear and they could be exceeded on downwind on the go around so they will raise the gear as they don't want to overspeed it.. The last thing you want is a configuration change when you are low and slow waiting for the turbine to spool up.. even changing the flaps can be a disaster.. the thing was flying when you decided to waive off... keep flying it get it climbing out then MAYBE think about doing something...
Old 12-12-2016, 07:40 PM
  #10  
ChicoFlyer
 
Join Date: Nov 2013
Location: Fair Oaks, CA
Posts: 144
Likes: 0
Received 0 Likes on 0 Posts
Default

This is just a hunch, but I also suspect a huge difference is in the way a fighter jet and our models produce usable thrust for aborted landings/takeoffs.

Model turbines have thrust that is related to the rpm of the engine, so when you need more thrust, it takes a moment to spool the turbine to the given required rpm.

A fighter jet has a nozzle on the turbine that can control thrust to a certain extent. In all of the videos I've seen of fighter jets on landing approach, the nozzle is as open as can be to lower thrust, in case of an aborted landing, upon throttling up, the nozzle would react much quicker and close to increase the thrust of the engine. There was a video recently posted of the very first F-16 flight, which happened completely on accident due to a malfunction. When the pilot went to reduce the throttle, the nozzle did not open up to allow an immediate decrease in thrust.

This is my amateur assumptions, there are plenty of people on these forums with actual jet experience that I'm sure would be thrilled to enlighten us in the differences of the engines we use. And I would love for them to confirm my suspicions, or tell me I'm full of crap.

Cheers,
Jason
Old 12-12-2016, 09:07 PM
  #11  
roger.alli
 
roger.alli's Avatar
 
Join Date: Aug 2008
Location: Sydney NSW , AUSTRALIA
Posts: 1,016
Received 1 Like on 1 Post
Default

When I make a decision to abort a landing,---- I go to full throttle, ----and then do nothing else but concentrate on flying the model. I try and get airspeed on as quickly as possible by lowering the nose before climbing out.. Usually an abort decision is made when I am low, slow, and badly positioned, which requires my full attention.

My problem is, I don’t make the abort decision early enough, if at all.. I tend to get into the “land at all costs” mind set, especially when flying my more precious models..
Old 12-14-2016, 07:25 PM
  #12  
tp777fo
My Feedback: (28)
 
tp777fo's Avatar
 
Join Date: Feb 2002
Location: Greer, SC
Posts: 3,357
Received 57 Likes on 42 Posts
Default

If you want to move something program t/o flaps to full throttle with gear down. In the big ones we start the flaps up with full throttle on go around to reduce drag. Gear stays down till positive climb just in case of a touchdown during the go around.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2022 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.