Maximum Forward Speed

[timwinters]

99% of all landings I make are short field. Minimum speed, minimum amount of runway used. Practice short field every time regardless of whether there is 1,000' or 10,000' of ruway in front of me. But then...

Okay, call me irresponsible, call me reckless, call me…well…whatever you want to call me, BUT, when I’m returning to my home ‘drome (KSGF), my three favorite words to hear from approach control is “MAXIMUM FORWARD SPEED” especially when followed by “to the runway.” It typically goes something like this:

So, I’m coming in from the NW at 5500’ last week, I check ATIS and, amongst other things, it reports the active runway to be 14. I contact approach 20 miles out and shortly thereafter I’m cleared for a straight in approach to 14 and I’m also told “maximum forward speed to the runway if possible”.

Whoo…hooo!

IF THE AIR IS SMOOTH….I give it to them…TO THE RUNWAY! Smooth air is very important, one big bump and the rest of this game is cancelled.

There’s no backing off the throttle for descent, instead I simply roll the trim down to achieve about 500 FPM at cruise power (20/2300 in my case). I then closely watch airspeed and my descent rate. I maintain indicated airspeed at the top of the green (160mph) throttling back only if necessary to keep the speed below the yellow arc and a descent rate of 500 to 700 fpm.

All the way to the runway.

Not all the way to final…not all the way to short final…but all the way to the numbers!

Then, with 8000’ of pavement in front of me I cut the throttle at the numbers, level the aircraft (about 10’ above the runway) and start to bleed off the airspeed. I hold it there and once I hit the white arc, start adding flaps. I continue to hold the airplane about 5’ to 10’ off the runway until all the excess airspeed is gone and we land.

I pull off and still have 3000’ of runway in front of me.

Know your airplane.

Fly your airplane.

Know exactly what your airplane will and will not do for you.

And, most importantly, have fun when ATC tell you to.

I do!

 

[ScottM]

Like you most all of the time I am landing for short field. I only go max speed when so directed and with enough runway to make it safe. I see nothign wrong with what you are doing.

 

[flyersfan31]

If I'm going into a C or (very rarely) B airport, I'll keep speed up even if they don't ask me to. Then I pretty much do as you do. I find it kind of relaxing to have all that runway to work with at the big airports!!!!

 

[dmccormack]

If I'm going into a C or (very rarely) B airport, I'll keep speed up even if they don't ask me to. Then I pretty much do as you do. I find it kind of relaxing to have all that runway to work with at the big airports!!!!

All pilots eventually need to be able to perform this adjustment -- but only after some experimentation and practice.

I've been told to keep the speed up in IMC on an ILS with 300' / 1 mile. I gave them 130 and that was enough.

 

[ScottM]

All pilots eventually need to be able to perform this adjustment -- but only after some experimentation and practice.

No kidding. I once was in a 172RG and told the keep the speed up. I had that baby at yellow line, 140kts. Slowing that down was fun!!! Putting out 40 degrees of flaps form zero flap at the top of the white line is an interesting adventure in trim, control pressure and level flight. Getting that gear down really get the L/D to decrease!!

 

[TMetzinger]

In the M20J, when asked, I'd give 150+ knots all the way to 1/2 mile short final, clean, then pop the speed brakes, hit the gear and flaps at appropriate speeds, and be doing less than 80 over the threshold.

In a 182, I can do something similar, as it will slow down quite nicely when the power is rolled off.

 

[dmccormack]

The A36 gets draggy enough with gear and flaps out to decelerate from 130 or so to 70 (over the fence light weight short field speed).

Much over 75 and she floats like a rubber duck.

I learned yesterday that the Skipper is a floater as well. Experimented with 65 as final speed (63 @ gross is book speed).

It felt like I floated 500 feet.

I'll use 60 KIAS from now on when solo, 63 when double.

 

[KennyFlys]

Best forward speed is a nice thing at larger airports and much appreciated by some of us. But also, please consider where you touch down and begin taxiing toward the turnoff.

At AUS when 35 is in use, the right side is currently not available due to construction on the approach end. So, all us little guys mix it up with the big guys on 35L. There aren't a lot of commercial flights but enough. They make up about 45% of the airport's operations.

35L is 12,000 and the first taxiway beyond the approach end is not until nearly 6,000 feet down the runway. Last week, I slowed down to barely 60 kts to avoid a left 360 and further delay. Another school's plane touched down on the numbers than taxied a slow speed for the remaining five thousand feet until the turn off. Imagine how ticked off that SWA captain would be were he the one to go around? That Diamond student or CFI may someday be headed for the big iron. I hope he remembers that action.

 

[dmccormack]

Best forward speed is a nice thing at larger airports and much appreciated by some of us. But also, please consider where you touch down and begin taxiing toward the turnoff.

Excellent point.

My student came to me from another school and a landing didn't count unless it was "on the numbers."

After a few brushes with trees and a few LONG taxis down the runway, we talked about what made sense given the conditions, the airport, the airplane, and the pilot.

I understand the need to put it on the numbers as required.

But like everything else in flying and in life, ya gotta be able to adapt.

 

[KennyFlys]

Excellent point.

My student came to me from another school and a landing didn't count unless it was "on the numbers."

After a few brushes with trees and a few LONG taxis down the runway, we talked about what made sense given the conditions, the airport, the airplane, and the pilot.

I understand the need to put it on the numbers as required.

But like everything else in flying and in life, ya gotta be able to adapt.

You just pick a point down the runway that correlates with the expected turn off. Pick a specific runway remaining sign. One can still practice accurate landings and it doesn't have to be on the numbers. Heck, treat it as a displaced threshold five thousand feet down. That works.

 

[flyersfan31]

I figured aiming for a quick turnoff went without saying. In addition to wanting you #1 for landing for as short a time as possible, it's a given that they want you off that runway ASAP!!!!!

 

[Skip Miller]

level the aircraft (about 10’ above the runway)

Tim, I do basically what you said, with one exception. I level off at about 50 feet not at 10 feet to ensure I am out of ground effect, until normal short approach speed. This maximizes drag and gets me down and off the runway more quickly. Most of the time I receive "Max forward speed", it is because the heavy iron is right on my tail.

-Skip

 

[Ken Ibold]

I got my favorite local approach the other day. Seems like I often get this when approaching from the north or northeast on an IFR flight plan with a visual approach in the offing. Jax approach keeps me at 3000 feet until a mile out and then clears me for a left downwind to Rwy 5 at CRG. Can't extend the downwind because there's a bevy of 1500 foot towers a couple miles away from the airport basically on the extended runway 23 centerline. So I yank up the nose to get down to gear extension speed, pop the gear and one notch of flaps. Then drop the nose and point it downwind, getting to midfield downwind at about 1500-2000 feet, depending on the wind. Put in another notch of flaps. At a normal base position but still at 1000 feet or more, crank in a 60 degree bank and watch the altimeter unwind. That puts me at a 3/4 mile final, 300 feet, 90 knots. Perfecto for a squeaker.

Not to say I always squeak it, but at least I'm set up to!

 

[poadeleted20]

20/2300 and cruise speed to the numbers followed by a chop to idle? Ooohhhh, I'd hate to be your engine -- that would hurt.

 

[Teller1900]

As Felix can attest, the 1900 is the King of "Best Forward Speed." Stay on the glideslope, holding 230-240kts (or 200 if we're at a C or D airport) to 1500 AGL, power to flight idle, props slowly forward, gear and flaps on speed, and a lot of nose up trim...you'll be on speed, on the slope with the "before landing checklist" complete by 500 AGL, and have it on the ground in the first half of the TDZ. I can't imagine how much a piston engine would hate us, though.

 

[bsdunek]

I figured aiming for a quick turnoff went without saying. In addition to wanting you #1 for landing for as short a time as possible, it's a given that they want you off that runway ASAP!!!!!

Just what I always thought. I try to land so I can make a turn off without smoking the brakes. Others may want to use the runway!

 

[timwinters]

I figured aiming for a quick turnoff went without saying. In addition to wanting you #1 for landing for as short a time as possible, it's a given that they want you off that runway ASAP!!!!!

 

[fgcason]

Until you're clear of the runway, they can't put anyone in behind you for the most part. I haven't timed it however I can slow down at 1/3 to 1/4 mile from the threshold and be off the runway quicker than I can float 3000ft down the runway before touching down then stopping then exiting.

I help out whenever possible and will keep moving best I can all the way down to about 300-400ft and/or short final with the runway in my face. Below or closer than that, it's my plane and my ASI, not theirs.

 

[TMetzinger]

20/2300 and cruise speed to the numbers followed by a chop to idle? Ooohhhh, I'd hate to be your engine -- that would hurt.

Define hurt in cooling rate in degrees per minute or second, please. I ask because in the mooney AND the C182 I've had engine monitoring, and the cooling rate never triggered the alarm (set to 50 degrees) on either one.

I'm not in the "shock cooling is a myth" camp, but before we can argue the point, we gotta define what constitutes an excessive cooling rate.

 

[poadeleted20]

Define hurt in cooling rate in degrees per minute or second, please.

I think the engine mfrs will tell you it's somewhere around 60-100 deg/min for ring/wall wear issues. Any good metallurgist will probably tell you it takes hundreds of degrees per second to cause immediate quench cracking, and short of dropping the hot engine in a cold oil bath, I don't think you can achieve that rate.

I ask because in the mooney AND the C182 I've had engine monitoring, and the cooling rate never triggered the alarm (set to 50 degrees) on either one.

Do you fly approaches at 20/2300 and then chop from there to idle over the numbers?

 

[dmccormack]

Define hurt in cooling rate in degrees per minute or second, please. I ask because in the mooney AND the C182 I've had engine monitoring, and the cooling rate never triggered the alarm (set to 50 degrees) on either one.

I'm not in the "shock cooling is a myth" camp, but before we can argue the point, we gotta define what constitutes an excessive cooling rate.

You beat me to this, Tim.

I had the same question -- though I am not in the 23"/2300 RPM all the way to 200' AGL camp.

I maintain cruise speed by reducing power gradually and pitching forward while letting gravity pick up the slack. It's very rare the air isn't bumpier down low while smooth up high, and the yellow arc is no where to be during descent.

I try to reduce power by 1" a minute, but have to admit I'm 100% consistent on that. I think that's a bit over-cautious for a normally aspirated piston like the IO-520/550 or O-470, but makes plenty of sense in a turbocharged airplane.

Typically in the A36 on a "maintain speed on final" approach, the engine has been loping along at 19"-20"/2300 RPM. The JPI has never indicated a sudden temp change (in excess of 50), even when doing the pull to idle, drop the flaps and land manuever. In fact IIRC, I've never seen more than 20 degrees Delta.

 

[TMetzinger]

No, I flew them starting at 24/2400 and then slowed (maintaining top of the green)at 1/2 mile final. Temps didn't exceed 50 dfpm. Certainly didn't YANK the throttle back, but still a lot of change in little time.

PS - why doesn't shutdown (where we see cooling of 100+ dfpm) cause problems? Is it because the engine isn't turning, so no valve/ring/wall issues?

 

[poadeleted20]

No, I flew them starting at 24/2400 and then slowed (maintaining top of the green)at 1/2 mile final. Temps didn't exceed 50 dfpm. Certainly didn't YANK the throttle back, but still a lot of change in little time.

As you said, the temp change didn't exceed 50 deg/min -- that may be a lot in your book, but it's not over the line drawn by the mfrs.

PS - why doesn't shutdown (where we see cooling of 100+ dfpm) cause problems? Is it because the engine isn't turning, so no valve/ring/wall issues?

Exactly. The problems are due to the heads shrinking enough faster than the pistons/valves that there is excessive wear. If the parts ain't moving, there's no wear, and the clearances will reappear as the engine cools further after shutdown.

 

[ScottM]

N

PS - why doesn't shutdown (where we see cooling of 100+ dfpm) cause problems? Is it because the engine isn't turning, so no valve/ring/wall issues?

Exactly. The problems are due to the heads shrinking enough faster than the pistons/valves that there is excessive wear. If the parts ain't moving, there's no wear, and the clearances will reappear as the engine cools further after shutdown.

Conceptually I have no problem with this. I am then starting to think about a warm start.

At a cold start everything is stabilized and the clearance are workable and warm up at about the same rate thus preserving those clearances.

It would seem that during a warm start there is more likely a chance that different parts of the engine will have cooled significantly than other parts and that a possible serious out of tolerance problem could occur. Thus there would be more wear during a warm start than during a cold start.

Say for instance if the cylinder heads have cooled but the pistons had not. You would be shoving a larger than usual piston up a smaller cylinder. Of course this probably is why the piston are sized as they are and the rings as they are.

 

[CJones]

I got my favorite local approach the other day. Seems like I often get this when approaching from the north or northeast on an IFR flight plan with a visual approach in the offing. Jax approach keeps me at 3000 feet until a mile out and then clears me for a left downwind to Rwy 5 at CRG. Can't extend the downwind because there's a bevy of 1500 foot towers a couple miles away from the airport basically on the extended runway 23 centerline. So I yank up the nose to get down to gear extension speed, pop the gear and one notch of flaps. Then drop the nose and point it downwind, getting to midfield downwind at about 1500-2000 feet, depending on the wind. Put in another notch of flaps. At a normal base position but still at 1000 feet or more, crank in a 60 degree bank and watch the altimeter unwind. That puts me at a 3/4 mile final, 300 feet, 90 knots. Perfecto for a squeaker.

Not to say I always squeak it, but at least I'm set up to!

Hmmm.. You would think you had a ton of Pitts time or something.

 

[poadeleted20]

Conceptually I have no problem with this. I am then starting to think about a warm start.

At a cold start everything is stabilized and the clearance are workable and warm up at about the same rate thus preserving those clearances.

It would seem that during a warm start there is more likely a chance that different parts of the engine will have cooled significantly than other parts and that a possible serious out of tolerance problem could occur. Thus there would be more wear during a warm start than during a cold start.

Say for instance if the cylinder heads have cooled but the pistons had not. You would be shoving a larger than usual piston up a smaller cylinder. Of course this probably is why the piston are sized as they are and the rings as they are.

Everything heats up fast enough on start that this isn't a significant problem.

 

[flyingcheesehead]

No, I flew them starting at 24/2400 and then slowed (maintaining top of the green)at 1/2 mile final. Temps didn't exceed 50 dfpm. Certainly didn't YANK the throttle back, but still a lot of change in little time.

I don't have any fancy engine monitoring stuff, but I do this sort of thing all the time and have a TBO+900 engine to show for it. I wouldn't do this on a big firebreathing turbo, but the O-470 is a pretty solid engine.

Okay, call me irresponsible, call me reckless, call me…well…whatever you want to call me, BUT, when I’m returning to my home ‘drome (KSGF), my three favorite words to hear from approach control is “MAXIMUM FORWARD SPEED” especially when followed by “to the runway.” It typically goes something like this:

I started doing max forward speed approaches in to about 3/4 mile at the home drome (KMSN/class C) quite a while ago. It's a good trick to have in the book, and the 182 is, of course, always happy to slow down.

Know your airplane.

Fly your airplane.

Know exactly what your airplane will and will not do for you.

Amen to that. I think that's what makes a pilot into a good pilot. You can practice PTS type maneuvers all you want, but I've found that what has made me a better pilot is to practice real-world things so I can learn the true answers to questions like "How close in can I do a max-forward-speed approach and still land in the touchdown zone?" and "How good is my actual glide performance?" I'm trying to come up with a whole list of such things...

 

[ScottM]

Everything heats up fast enough on start that this isn't a significant problem.

I doubt that it heats up fast enough when immediately after start up the engine is idling at least a 1000rpm. That is stuffing a skinny cooler cylinder with a fat hot piston once every 4.2 seconds. If the engine took as little as 10 seconds to heat back up then that piston would be in there at least twice.

I think it has more to do with the amount of tolerance that each of the piston rings can deal with such that the piston is never too large and that the rings take up or give up slack surrounding the piston.

I would also imagine that cylinder position and piston parking location in the non-running condition would also all play a part. Hmmm and interesting thermal simulation to ponder.

 

[poadeleted20]

I doubt that it heats up fast enough when immediately after start up the engine is idling at least a 1000rpm.

Yes, it does. The heating is applied evenly to both the piston and the inside of the cylinders. The cooling is taken off the outside of the cylinders and the pistons have to transfer their heat through the cylinder bodies. That's the difference.

 

[ScottM]

Yes, it does. The heating is applied evenly to both the piston and the inside of the cylinders. The cooling is taken off the outside of the cylinders and the pistons have to transfer their heat through the cylinder bodies. That's the difference.

Heat transfer is never instantaneous.

For some period of time, whether a cold start or a hot start, the engine components are not up at a fully stable temperature. During that time design considerations must take into this into account and each component must have the tolerances to deal with the variations.

 

[poadeleted20]

Heat transfer is never instantaneous.

Exactly, and that's why the heating process from the inside is more even than the cooling process from the outside.

For some period of time, whether a cold start or a hot start, the engine components are not up at a fully stable temperature. During that time design considerations must take into this into account and each component must have the tolerances to deal with the variations.

Agreed, but for the reasons stated, rapid external cooling causes ring/wall and stem/guide wear, and internal heating doesn't.

 

[TMetzinger]

Exactly, and that's why the heating process from the inside is more even than the cooling process from the outside.

Now THAT statement doesn't make sense to me - physically, heat transfer is heat transfer, either it's a + or -, but that's it.

There's no real consensus on shock cooling, other than the generic "gradual changes in temperature are better than rapid".

If shock cooling were an absolute, then you'd expect to see engines used for ME training (where they get shut down in flight frequently, or at least reduced to idle power) having horrible failure rates, and that hasn't happened.

I'll also grant that lower powered engines probably have it easier, and the Mooney J model and 182 are actually both pretty "beefy" for the horsepower, and CHTs don't seem to run too hot on them when they are making power A turbocharged model, or a 300 horse engine might be a different story.

 

[poadeleted20]

Now THAT statement doesn't make sense to me - physically, heat transfer is heat transfer, either it's a + or -, but that's it.

In the cooling situation, the cylinder is cooled from the outside, while the pistons must transfer their heat to the cylinders before that heat is dumped. Thus, the cylinder cools more quickly and shrinks from the outside. The heat is supplied from the inside, and equally applied to both cylinder (on the inside face) and piston, thus, they heat together.

 

[timwinters]

20/2300 and cruise speed to the numbers followed by a chop to idle? Ooohhhh, I'd hate to be your engine -- that would hurt.

I see the shock cool alarm go off far more often when I'm impatient once reaching cruise and reduce power and lean too quickly after a long climb. I've learned to wait a few minutes after a long climb before setting up cruise power. In this case my CHT's will be approaching 400dF and the OAT may be 40dF. that's a substantial delta t.

Conversely, I rarely see my shock cool alarm go off when chop power for descent. This is true whether it's 1", 5" or full chop (down low) and I have my alarm set at 25dF. (EI UBG16).

But, and I think this is a big factor as to why...

I have the last model year of 182's with no cowl flaps so my engine's being excessively cooled all the time at cruise settings. I rarely see cruise CHTs of over 325dF, the front two cylinders are always below 300dF (heck, as stated above I have to climb HARD to reach 400dF on any cylinder even on a hot day). It's hard to shock cool an engine that's already that cool when the air temp is 90dF (or 120dF immediately above the runway asphalt). That's a much smaller delta t than as outlined above thus producing much slower cooling.

But, your point's well taken. It's probably not a good on the engine on any day but especially on cold winter day when more cooling capacity is available at the surface.

 

[flyingcheesehead]

I see the shock cool alarm go off far more often when I'm impatient once reaching cruise and reduce power and lean too quickly after a long climb. I've learned to wait a few minutes after a long climb before setting up cruise power. In this case my CHT's will be approaching 400dF and the OAT may be 40dF. that's a substantial delta t.

Tim,

What power settings do you use for climb, cruise, and descent? I don't have any fancy engine monitors, just the original gauges.

I use WOT/2500 for climb and (unless I'm way down low) WOT/2300 for cruise, leaned to 1305dF EGT.

 

[timwinters]

Kent,

I climb WOT all the way to altitude, RPM backed off of redline (2550 or so).

I cruise at 20"/2300RPM, 50dF carb heat, lean till rough, enrichen to smooth. This keeps me below 65% power so I can aggressively lean w/o fear of engine damage. I burn 10 to 11 gph and average about 128kts (true airspeed) depending on altitude. I can pick up about 12kts by running 23/2300 and leaning to 125dF ROP but I'll burn 14 to 15 GPH and it's just not worth it to me.

My typical descent (if not asked for max forward speed) is to pull 2.5" and then pull another 2.5" about 2 minutes later. I'm not sure about other birds but in a 182 you'll descend 100fpm for every inch of MP you pull (without touching the trim or anything else). So, pull 5" and you'll descend 500fpm and remain at the same speed as you were cruising at.

That's how I usually fly...but I'm typically not in a big hurry.