Arrow best glide and gear down?

S

scooter

Pre-Flight
Joined
Nov 24, 2006
Messages
32
Display Name
Display name:
Scooter
In the Arrow III (PA28R-201), per POH, best glide is 79kts with gear up and flaps up.

If the landing gear is extended (but flaps remain retracted), what would happen to the best glide speed?
 
Why would you EVER want best glide with gear down?

If you want distance, leave the gear up.

Lower the gear when the field is "made" (or you're otherwise committed to a landing), along with the flaps.

FWIW, a decent approximation for dirty best glide is the short field approach speed.
 
If memory serves, the Cherokee 180 and Archer are both very close to 80kt, and those are basically identical airframes to a gear-down arrow. The gear would add drag, obviously, but I doubt your best glide would change by much.

Also, what MAKG said. Why would you ever do this?
 
The-Flying-Lawyer said:
Why would you ever do this?
Click to expand...
In some circumstances the pilot might not have a choice, so it's a worthwhile question to ask. I once had a hydraulic system fail in flight in a Turbo Arrow. The gear just plopped down and stayed there because there was no hydraulic pressure to keep it retracted. The manual doesn't say anything about change in best glide speed with the rollers out.
 
That's true. I guess the other scenario I could see would be losing alternator at high altitude on an electric-gear plane. Depending on how much faith you had in the backup gear system I could see it making sense to burn the juice and get the wheels down awhile before they're needed.
 
Pilawt said:
In some circumstances the pilot might not have a choice, so it's a worthwhile question to ask. I once had a hydraulic system fail in flight in a Turbo Arrow. The gear just plopped down and stayed there because there was no hydraulic pressure to keep it retracted. The manual doesn't say anything about change in best glide speed with the rollers out.
Click to expand...

As a comparison the best glide on the 'kota is 86. I think the 'kota is identical to the Arrow III except for the gear and cowl.

It might be interesting to do a little experimentation with an Arrow to see if best glide varied much for gear-up vs gear-down.
 
MAKG1 said:
Why would you EVER want best glide with gear down?
Click to expand...

This came up in a discussion around the power off 180 approach to landing maneuver for the commercial certificate.

In that situation the gear goes down abeam (or earlier) the touchdown point.
 
scooter said:
This came up in a discussion around the power off 180 approach to landing maneuver for the commercial certificate.

In that situation the gear goes down abeam (or earlier) the touchdown point.
Click to expand...

In the Arrow III, I always pitched for 79kts on the 180.
 
scooter said:
In the Arrow III (PA28R-201), per POH, best glide is 79kts with gear up and flaps up.

If the landing gear is extended (but flaps remain retracted), what would happen to the best glide speed?
Click to expand...

Anything that increases parasite drag will decrease best glide speed (as well as glide ratio, obviously).
 

Attachments

  • airspeed-drag.png
    airspeed-drag.png
    25.5 KB · Views: 39
Clark1961 said:
As a comparison the best glide on the 'kota is 86. I think the 'kota is identical to the Arrow III except for the gear and cowl.

It might be interesting to do a little experimentation with an Arrow to see if best glide varied much for gear-up vs gear-down.
Click to expand...

The Arrow glide ratio with the gear down will probably be worse than a Dakota due to drag from the doors and wells.
 
Clark1961 said:
As a comparison the best glide on the 'kota is 86. I think the 'kota is identical to the Arrow III except for the gear and cowl.



It might be interesting to do a little experimentation with an Arrow to see if best glide varied much for gear-up vs gear-down.
Click to expand...

Interesting.

As I recall, the Warrior II, the Arrow III and the Dakota all have the same wing.

Best glide in the Warrior is 73, 79 on the Arrow and you say 86 for the Dakota.

Sounds like best glide is related to aircraft weight.
 
Fearless Tower said:
Interesting.

As I recall, the Warrior II, the Arrow III and the Dakota all have the same wing.

Best glide in the Warrior is 73, 79 on the Arrow and you say 86 for the Dakota.

Sounds like best glide is related to aircraft weight.
Click to expand...
'Cept that Clark's Dakota is a PA-28-201T "Turbo Dakota", with the same gross weight as a Turbo Arrow. Pretty much apples 'n' apples except for the gear.
 
Pilawt said:
'Cept that Clark's Dakota is a PA-28-201T "Turbo Dakota", with the same gross weight as a Turbo Arrow. Pretty much apples 'n' apples except for the gear.
Click to expand...

Does the Turbo Arrow have the same best glide speed as the NA?
 
Fearless Tower said:
Does the Turbo Arrow have the same best glide speed as the NA?
Click to expand...
Apparently not -- 19 knots difference! I'd flown Turbo Arrow IVs a lot, but never the NA version, so I wasn't aware of the dichotomy. I just found this discussion about it on pprune, and they can't figure it out either:
http://www.pprune.org/private-flying/415672-glide-speeds-pa28r-versions.html

Arrow-S5-26.jpg


TurboArrow-SC5-4-2.jpg
 
Pilawt said:
'Cept that Clark's Dakota is a PA-28-201T "Turbo Dakota", with the same gross weight as a Turbo Arrow. Pretty much apples 'n' apples except for the gear.
Click to expand...

Yes, I have a turbo. the difference between the NA and turbo 'kota is 100 pounds gross weigth and a little cowl difference. I think the engines are about the same weight.
 
dmspilot said:
The Arrow glide ratio with the gear down will probably be worse than a Dakota due to drag from the doors and wells.
Click to expand...

Thats what I'm thinking. Perhaps the Arrow III best glide is with gear down.


On the 'kota, Vx is 75 and Vy is 90 so best glide of 86 fits. Be interesting to see the numbers for the Arrow.
 
If I'm not mistaken, to get the actual glide ratios listed in the performance graphs for the Arrow, you have to pull the prop back to the stop i.e. Low rpm, coarse pitch.

That's a bit hard when you've lost oil pressure. So, to be safe, drop a brick out the window and follow it.
 
The-Flying-Lawyer said:
That's true. I guess the other scenario I could see would be losing alternator at high altitude on an electric-gear plane. Depending on how much faith you had in the backup gear system I could see it making sense to burn the juice and get the wheels down awhile before they're needed.
Click to expand...

Why do you need best glide with an alternator or hydraulic failure? You would need a simultaneous engine failure to go there.
 
Find the best glide of a brick. It's the same as an Arrow with the gear down.
 
Fearless Tower said:
Sounds like best glide is related to aircraft weight.
Click to expand...
It does.

More weight requires more lift (and more induced drag) - take the induced drag / parasitic drag graph posted earlier in this thread and imagine the induced drag curve moved upwards.
 
Pilawt said:
In some circumstances the pilot might not have a choice, so it's a worthwhile question to ask. I once had a hydraulic system fail in flight in a Turbo Arrow. The gear just plopped down and stayed there because there was no hydraulic pressure to keep it retracted. The manual doesn't say anything about change in best glide speed with the rollers out.
Click to expand...

In most aircraft power is only required to bring the gear up.

Drop the gear when the field is made only.


Only other time I could imaging is for a emergency decent with the engine off (fire etc).
 
James331 said:
In most aircraft power is only required to bring the gear up.

Drop the gear when the field is made only.

Only other time I could imaging is for a emergency decent with the engine off (fire etc).
Click to expand...
In the PA-28R and PA-32R (maybe PA-34 and PA-44 also; I've not flown those), hydraulic pressure alone holds the gear up. Lose hydraulic pressure and gravity takes over.
 
Had the opportunity to fly in an Arrow last weekend. First time in anything other than a 172. Had a horrible time maintaining altitude once the gear came down. It's an entirely different type of flying!
 
I've had the, uh, pleasure of having a hydraulic line blow out on one of the mains, which led to a partial gear up situation. The gear dropped but not completely. It took me some time to figure out what was going on, but the emergency extension lever dumped the remaining pressure and the gear finally dropped in place.
 
The four of us had just taken off in a rented Turbo Arrow IV from Kingman, Arizona, returning to Van Nuys,on the last leg of an eleven-day, eleven-stop, vacation. Shortly after leveling off at cruise altitude, the big red "gear unsafe" light came on, followed a few seconds later by the left main "down and locked" green light. Airspeed and slipstream noise also confirmed gear was partially extended. I cycled the gear and all seemed cleaned up and normal, but within a few minutes the light show repeated, and this time both mains went down. The nose gear was stuck somewhere in transit.

I slowed way down and cycled the gear again, and this time got three green, and the red "unsafe" light finally went out. Finding this to be at least a more satisfactory state of affairs, I left it that way and we continued on gear-down to VNY.
 
MAKG1 said:
Why do you need best glide with an alternator or hydraulic failure? You would need a simultaneous engine failure to go there.
Click to expand...

Also true. I was definitely imagining a simultaneous all-system failure in my mind, which is obviously unlikely. That's another reason I want to keep training. Throughout your PPL training, you talk through all kinds of system failures, but one of the only knee-jerk "instincts" you viscerally develop is "pitch and trim for 80" (in the Cherokee) when the power gets pulled. I can still hear it ringing in my ears two years later.

Earlier this summer I lost power momentarily in a Skyhawk cruising at 7500'. My fuel burn was unbalanced even though the selector was on "both", so I wanted to even them out. I switched to the fuller tank, and had a sudden RPM drop a few seconds later. Without thinking, my left hand/eyes pitched for 65 kt. My right hand wandered to the fuel selector in another second or two and flipped it back to both. Power came back, flight went on smoothly.

Premature? Maybe. I probably could have solved the power loss quicker by thinking of the fuel before the airspeed. I still think it's a good reflex, as I'd rather give myself maximum time and then troubleshoot (even if it takes longer in the end).

I think developing those instincts is probably the single most important aspect of PPL training ("where'd the wind noise go? pitch down!" is another), and if I'm honest they aren't as strong on things like engine or electrical fire as the ones I "really" practiced. I always like having something to work on next time I'm up. :)
 
Figured I'd revive this thread instead of starting a new one (damned if you dont, damned if you do).
I'm working on getting all the arrows systems crammed in my head and knowing the speeds cold.
Everything is what I remember learning.... except best glide.
The plane: 1975 Arrow II (pa-28r-200, still has the Hershey bar wing)
When looking at the 'emergency procedures' section of the book it says to pitch for 110 mph ias.
In the 'performance charts' it says 105 mph ias.
Why the difference in the manual, and does the wing make that much of a difference between an arrow II best glide and an arrow III best glide?

Edit to add: in either case we put the gear override lever in the lock position to keep it from freefalling. Maybe that's the difference since the gear could drop out at 105 or below?
 
The-Flying-Lawyer said:
That's true. I guess the other scenario I could see would be losing alternator at high altitude on an electric-gear plane. Depending on how much faith you had in the backup gear system I could see it making sense to burn the juice and get the wheels down awhile before they're needed.
Click to expand...

Why?

If I was concerned at all about making the field, I'll err on the side of a gear up landing vs not making my landing.


Priorities (in order of importance)
Skin (your life)
Tin (the airplane)
Ticket (not pizzing off the feds)
 
farmerbrake said:
Figured I'd revive this thread instead of starting a new one (damned if you dont, damned if you do).
I'm working on getting all the arrows systems crammed in my head and knowing the speeds cold.
Everything is what I remember learning.... except best glide.
The plane: 1975 Arrow II (pa-28r-200, still has the Hershey bar wing)
When looking at the 'emergency procedures' section of the book it says to pitch for 110 mph ias.
In the 'performance charts' it says 105 mph ias.
Why the difference in the manual, and does the wing make that much of a difference between an arrow II best glide and an arrow III best glide?

Edit to add: in either case we put the gear override lever in the lock position to keep it from freefalling. Maybe that's the difference since the gear could drop out at 105 or below?
Click to expand...

Not sure about the specifics, but the wing makes a big difference in how a II flies vs. a III. A II drops faster, and is more forgiving on carrying excess airspeed in to the landing in terms of float.

Also I'm not surprised that a Turbo Arrow has a different best glide speed than a NA Arrow III even though they have the same wing and airframe. The cowlings are different, plus I believe the TA has a larger nosegear as well.
 
farmerbrake said:
When looking at the 'emergency procedures' section of the book it says to pitch for 110 mph ias. In the 'performance charts' it says 105 mph ias.
...
Edit to add: in either case we put the gear override lever in the lock position to keep it from freefalling. Maybe that's the difference since the gear could drop out at 105 or below?
Click to expand...

That is the reason.

farmerbrake said:
[D]oes the wing make that much of a difference between an arrow II best glide and an arrow III best glide?
Click to expand...

The longer wing produces more lift at lowe speeds, less induced drag and more parasite drag, so best glide speed should be lower. I don't have an Arrow III POH but I do have an Arrow IV one, the best glide speed is shown as only 79 KIAS (91mph).
 
The difference between the II and the III glide speeds have to do with the wing. YES, the aerodynamics of the taper wing versus the Hershey bar are that significant. The taper wing is a much better wing and I miss it(had it in my warrior II). But, I wasn't gonna pay a 20 k premium for it in the arrow III, so arrow II it was. Of course I would have also got a 72 gal usable with the III and thatd some long legs, but for my mission it was more of a nice to have than a must have.
 
dmspilot said:
That is the reason.



The longer wing produces more lift at lowe speeds, less induced drag and more parasite drag, so best glide speed should be lower. I don't have an Arrow III POH but I do have an Arrow IV one, the best glide speed is shown as only 79 KIAS (91mph).
Click to expand...
Now I feel like a dumb a$$ for not realizing that everyone in this thread was talking kts instead of mph.... stupid piper for having to make some things in mph...

Sent from my SAMSUNG-SM-N910A using Tapatalk
 
You must log in or register to reply here.
Back
Top