FAA AC 150/5380-9 explained: the Boeing Bump method, BBI and ProFAA for runway roughness

FAA Advisory Circular AC 150/5380-9 (Guidelines and Procedures for Measuring Airfield Pavement Roughness; 30 September 2009, no revision letter, Active) is the United States Federal Aviation Administration (FAA) document that sets out how runway bump roughness is measured and scored. It describes the Boeing Bump method, a ratio called the Boeing Bump Index (BBI), and the free ProFAA software that computes it (FAA, 2009) (FAA, 2024c). This guide explains what the circular is for, how it is organised, how the index works term by term, and what it leaves to other documents.

Key facts

• FAA Advisory Circular AC 150/5380-9 was issued on 30 September 2009 with no revision letter and is listed by the FAA as Active.
• AC 150/5380-9 defines runway roughness by its effects on the aircraft, not by passenger ride quality, and treats texture as separate from roughness.
• The Boeing Bump Index at a profile point is the largest ratio, over all straightedge lengths, of measured bump height to the height the acceptable zone allows at that bump length.
• A Boeing Bump Index below 1.0 lies in the acceptable zone, and a value above 1.0 lies in the excessive or the unacceptable zone, not simply the unacceptable one.
• The circular covers single events only, and a 2024 FAA research report (DOT/FAA/TC-24/14), which does not constitute FAA policy, recommends updating it and ProFAA to add multiple-event evaluation.
• The circular is not mandatory except for projects funded through the Airport Improvement Program or by Passenger Facility Charges, and it is engineering background rather than operational guidance.

What is AC 150/5380-9 and what status does it have?

AC 150/5380-9 is an FAA advisory circular, a guidance document, issued on 30 September 2009 with no revision letter; the FAA index lists it as Active. Paragraph 2 says it is not mandatory except for projects funded through the Airport Improvement Program (AIP) or by Passenger Facility Charges (PFC), the two US federal funding routes for airport work (FAA, 2009). It is not an International Civil Aviation Organization (ICAO) standard, and the BBI is an FAA index derived from Boeing criteria, not an ICAO quantity. For the limits that ICAO, FAA and EASA documents set, see the hub guide on runway surface thresholds.

What does the circular measure, and what does it leave out?

The circular defines airfield roughness by its effect on the aircraft, not on a passenger: fatigue and wear, cockpit vibration, excessive acceleration and reduced braking (para 1.2b to 1.2e). Texture is not roughness in this document (para 1.2g) (FAA, 2009). Its guidance rests on jet transports near rotation speed, quoted as 130 to 200 knots in para 2.1 (about 67 to 103 m/s, calc/bbi_placeholder.out.txt), for fully loaded jet transports, and it is described as conservative for taxiways and aprons.

The scope is single events. The Foreword says the circular does not address cyclic or harmonic events, and later FAA research recommends updating the circular and ProFAA to add multiple-event evaluation (FAA, 2024b). The frequency-domain alternative, the power spectral density, is not used by the circular; the PSD guide covers it.

Narrated film · 2:44

FAA AC 150/5380-9 explained

Narrated film built from the calc/ outputs; the allowable height is a placeholder, not the circular's curve.

Read the film transcript

One runway bump can matter more than a kilometre of gentle waves, so how does the FAA score it? Advisory Circular one fifty slash fifty-three eighty dash nine is the American guidance on measuring runway roughness. It was issued on the thirtieth of September, two thousand and nine, and is listed as active. It is mandatory only for projects funded through the Airport Improvement Program or by Passenger Facility Charges. It defines roughness by what it does to the aircraft, not by passenger comfort. That means fatigue and wear, cockpit vibration, excessive acceleration and reduced braking. The survey runs along the centreline and along offset lines chosen from the gear layout. An offset of three point zero five metres can address the smaller aircraft groups, and five point two two metres the larger ones. A virtual straightedge is laid between two profile points, and the bump height is the largest gap between surface and line. Bump length is the shorter distance to either end, so a bump at the middle of a twenty-four metre straightedge has a bump length of twelve metres. Now the Boeing Bump Index, one term at a time. BBI is the largest value, over every straightedge length L, of a ratio. On top is h of L, the measured bump height for that length. Underneath is h sub a of b, the height the acceptable zone allows at bump length b. For a bump at the middle, b equals L divided by two. Take one synthetic point, with a placeholder allowance of two and a half millimetres per metre of bump length. Sixteen metres gives nine over twenty, which is zero point four five. Twenty-four metres gives eighteen over thirty, or zero point six zero, and forty metres gives thirty-six over fifty, or zero point seven two. The largest ratio is zero point seven two, and a real sweep could find a larger one. A value below one lies in the acceptable zone. A value above one is excessive or unacceptable, so above one does not mean unacceptable by itself. ProFAA first filters the profile, and that filter has a gain. The cut-off wavelength lambda sub c is one divided by nu sub c, the cut-off of two cycles per metre, which gives half a metre. The gain G at frequency nu is one over the square root of one plus nu over nu sub c, to the power twelve. Plotted against wavelength, the gain is flat for long waves, zero point seven one at half a metre, and zero point zero one six at a quarter of a metre. Because the cut-off sits at the limit of the quarter-metre sampling, some content can still alias. The circular sets no spectral criterion, no wheel load limit, no roughness index limit and no closure decision for a given runway. It covers single events, and later FAA research recommends adding multiple events. This is engineering background, and operating decisions belong to the aerodrome operator.

How is the circular organised?

The circular follows a short path from definition to software.

• 1.2 defines roughness by aircraft effects.
• 2.1 gives the basis: critical bump height depends on how a wavelength relates to the aircraft's natural frequency, near rotation speed.
• 2.2 sets the survey parameters. The standard profile interval is 0.25 m (0.82 ft), and straightedges run from 0.5 m to 120 m (394 ft). Survey lines are the centreline and offsets either side, 3.05 m (10 ft) or 5.22 m (17.5 ft) by aircraft group (para 2.2f); the survey how-to works through them.
• 2.3 describes the zones.
• 2.4 defines the BBI, and 2.5 applies it.
• Chapter 3 describes ProFAA.

An airfield survey line is an offset chosen from gear geometry, not a painted lane, so the road wording of lane and wheelpath conventions does not transfer.

What is the Boeing Bump Index and how is it calculated?

The BBI scores each profile point by the largest ratio, over all straightedge lengths, of measured bump height to the height the acceptable zone allows at that bump length (para 2.4a, steps 1 to 4) (FAA, 2009). A virtual straightedge is laid between two profile points. Bump height is the largest deviation of the surface from it. Bump length is the shorter distance from the bump to either end, so a bump at the middle of a 24 m straightedge has a bump length of 12 m.

The allowable heights come from a curve in Figure 2-3 with polynomial fits in para 2.4b. This guide does not reprint that curve; its shape is that the allowable height rises with bump length, and the worked example below uses a placeholder instead.

The formula, term by term: Boeing Bump Index

Equation 1: BBI = max over L of [ h(L) ÷ hₐ(b) ], with b = L ÷ 2 for a bump at the middle of the straightedge.

symbol	what it is in words	unit	where its value comes from	typical range
BBI	the index at one profile point	dimensionless	the result of Equation 1	below 1.0 is the acceptable zone (para 2.4a, 2.5a)
L	straightedge length	m	chosen by the sweep (para 2.2)	0.5 m to 120 m
h(L)	measured bump height	mm here (the circular states bump height in centimetres, para 2.2d(1), 2.4b; Fig 2-3 axis in cm)	the profile, against that straightedge	synthetic here
b	bump length	m	the shorter distance to a straightedge end	up to 60 m on Figure 2-3
hₐ(b)	upper limit of the acceptable zone at b	mm	Figure 2-3 and para 2.4b; a placeholder here	placeholder, 2.5 mm per metre

Where it comes from. This is a defined index, not a derived law, and it is empirical in origin. Figure 2-3 reproduces Figure 10 of Boeing D6-81746. Boeing based the criterion on operational experience with single bump events, and the circular says the criterion does not give a detailed analysis of airplane response (para 2.3a). The circular's steps are:

1. Lay a straightedge of length L over the profile.
2. Take the bump height h and bump length b.
3. Divide h by the allowable height at b.
4. Repeat for every L and keep the largest ratio.

Worked numbers. The profile point and heights are synthetic, and the allowable height is a placeholder that is not the AC curve, set at 2.5 mm per metre of bump length.

• L = 16 m, so b = 8 m: 9.0 mm ÷ 20.0 mm = 0.45.
• L = 24 m, so b = 12 m: 18.0 mm ÷ 30.0 mm = 0.60.
• L = 40 m, so b = 20 m: 36.0 mm ÷ 50.0 mm = 0.72.

Of the three lengths tried, the largest ratio is 0.72, so the BBI analogue at this point is 0.72. The real method sweeps every straightedge length, which is 479 at the FAA standard interval (para 2.2d), so a sweep could find a larger ratio (calc/bbi_placeholder.out.txt).

What it means and where it stops. The result says which straightedge length, here the 40 m one with a 20 m bump length, gives the governing ratio at that point. Para 2.2b uses "bump length" in place of "wavelength" for this method, so a straightedge length is not a wavelength band. It is valid for single events on one survey line. Two misreadings are common. The ratio is not a wheel load, and a value with the placeholder says nothing about a real runway. The circular's own application is in para 2.4a and 2.5a. ProFAA searches for the combination that gives the largest BBI, not necessarily at a local maximum or minimum (para 2.4d).

What do the zones mean, and what is often misread?

The circular draws three zones on Figure 2-4: acceptable, excessive and unacceptable. A BBI below 1.0 is in the acceptable zone, and a BBI above 1.0 is in the excessive or the unacceptable zone (para 2.4a, 2.5a) (FAA, 2009). The circular gives no single BBI value for the boundary between excessive and unacceptable. It defines that boundary as the upper-limit curve of para 2.4b(2), and Figure 2-4 redraws it as BBI against bump length (para 2.5a); this guide does not reprint the curve. In para 2.3b(2) and 2.3b(3) it states that excessive roughness needs immediate repair though closure is not required, while unacceptable roughness warrants immediate closure of the affected pavement. These are the circular's zone definitions, quoted as such.

Four misreadings recur.

1. "BBI above 1 means unacceptable." It means excessive or unacceptable; the circular names two zones above the line.
2. "120 m and 60 m conflict." The longest straightedge is 120 m, but a bump at its centre has a bump length of 60 m, the limit plotted in Figure 2-3.
3. "Three zones everywhere." Transport Canada's AC 302-023 (Issue 02, 16 December 2016) draws four regions in para 6.1(4) (Transport Canada, 2016).
4. "One smoothness figure." The circular cites an earlier edition's straightedge tolerance (para 2.3b(1)), and a later FAA specification (AC 150/5370-10H, 2018) uses a different straightedge length; the hub sorts the two.

This is engineering background, not operational guidance. Decisions to operate, restrict or close a runway belong to the aerodrome operator under its State's rules.

What does ProFAA do with a profile?

ProFAA is the FAA's free software for computing the BBI and other indices from a measured profile. Chapter 3 of the circular says it low-pass filters the profile with a sixth-order Butterworth filter at 2 cycles/m and decimates it to 0.25 m (AC 150/5380-9 3.2) (FAA, 2009). A low-pass filter passes long wavelengths and attenuates short ones. As described in the 2023 FAA research report, ProFAA's equations of motion did not allow variable speed, which take-off and landing simulations need, and it used one survey line (FAA, 2023). At that time it therefore did not simulate the take-off roll. A 2024 FAA report recommends updating the circular and ProFAA to add multiple-event evaluation (FAA, 2024b).

The formula, term by term: filter cut-off wavelength

Equation 2: λ_c = 1 ÷ ν_c, and the gain is G(ν) = 1 ÷ √(1 + (ν ÷ ν_c)¹²).

symbol	what it is in words	unit	where its value comes from	typical range
λ_c	wavelength at the cut-off	m	Equation 2	0.5 m here
ν_c	spatial cut-off frequency	cycles/m	AC 150/5380-9 3.2	2 cycles/m
ν	spatial frequency of a profile component	cycles/m	1 ÷ its wavelength	any
G	ideal filter gain, output ÷ input amplitude	dimensionless	ideal sixth-order Butterworth response	0 to 1
Δx	retained sample interval	m	AC 150/5380-9 3.2	0.25 m

Where it comes from. Spatial frequency is the number of wave cycles per metre, so it is the reciprocal of wavelength; that is a definition. The gain expression is the magnitude response of an ideal sixth-order Butterworth filter, the twelfth power coming from twice the order. The circular does not say how ProFAA implements the filter digitally, or whether it filters forward and backward; a forward-and-backward pass would square the gain, giving 0.5 at the cut-off. A profile sampled every Δx cannot represent wavelengths below 2Δx, the Nyquist limit. Both results are derived, not empirical.

Worked numbers. The cut-off is ν_c = 2 cycles/m, so λ_c = 1 ÷ 2 = 0.50 m. With Δx = 0.25 m, the Nyquist wavelength is 2 × 0.25 m = 0.50 m, which equals the cut-off wavelength. A -3 dB cut-off placed at Nyquist is not a complete anti-alias guard, because the filter still passes 0.71 of the amplitude there. The ideal gain is 0.7071 at 0.50 m, 0.9999 at 1.00 m, 0.0875 at 0.33 m and 0.0156 at 0.25 m (calc/bbi_placeholder.out.txt).

What it means and where it stops. Profile content shorter than about half a metre is strongly attenuated before the index is computed. The ideal gain is 0.71 at 0.5 m and 0.016 at 0.25 m, so little survives below about 0.3 m. Because the cut-off sits at the Nyquist frequency of the 0.25 m output, the part that passes between about 0.33 m and 0.5 m can alias into longer wavelengths after decimation. The roll-off is gradual: a filter does not cut sharply at 0.5 m. The filter belongs to this method, and it is not a statement about what an aircraft ignores.

What does the circular not decide?

The circular sets no power-spectral-density criterion, no wheel-load limit and no International Roughness Index (IRI) limit, and it makes no closure decision for a specific runway. It also warns about high-pass-filtered inertial profilers for this use (para 2.2g). The comparison with other measures is in BBI vs IRI vs straightedge. The FAA's own research reports go beyond it, with Types 1, 2 and 3 roughness and multiple-event tools, and are research, not FAA policy (FAA, 2023) (FAA, 2024b). The loads behind the Boeing criterion are explored in the bump and gear-load guide.

Frequently asked

What is FAA AC 150/5380-9?

FAA Advisory Circular AC 150/5380-9, Guidelines and Procedures for Measuring Airfield Pavement Roughness, was issued on 30 September 2009 with no revision letter and is listed as Active. It describes how runway bump roughness is measured, the Boeing Bump Index (BBI) and its zones, and the ProFAA software. It is guidance, not mandatory except for AIP and PFC funded projects.

What does a Boeing Bump Index above 1.0 mean?

In AC 150/5380-9 (30 September 2009), a Boeing Bump Index (BBI) below 1.0 lies in the acceptable zone, and a value above 1.0 lies in the excessive or the unacceptable zone. It does not mean unacceptable by itself. The circular's zone definitions, in paragraphs 2.3b(2) and 2.3b(3), are engineering background, and operating decisions belong to the aerodrome operator.

What does ProFAA do with a runway profile?

ProFAA is the FAA's free software for runway roughness indices. Chapter 3 of AC 150/5380-9 says it low-pass filters the profile with a sixth-order Butterworth filter at 2 cycles/m and decimates it to 0.25 m. As described in a 2023 FAA report, its equations of motion did not allow variable speed and it used one survey line, so at that time it did not simulate the take-off roll; a 2024 FAA report recommends adding multiple-event evaluation.

What does AC 150/5380-9 not decide?

AC 150/5380-9 sets no power spectral density criterion, no wheel-load limit, no International Roughness Index limit and no closure decision for a particular runway. It addresses single events, not cyclic or harmonic ones. FAA research reports on multiple-event roughness go further but are research, not FAA policy.

Where this connects

The next documents to meet are the limits in the hub guide on runway surface thresholds and the field method in the runway roughness survey how-to. On the road side, the same profile physics is checked in the validation-section guide and in TMH 13 automated assessments.

References

1. FAA (2009). AC 150/5380-9, Guidelines and Procedures for Measuring Airfield Pavement Roughness. 30 Sep 2009, no revision letter, Active. Original source.Foreword; para 1.2b-g; para 2; 2.1; 2.2a-g; 2.3a-b; 2.4a-d; 2.5a-b; Fig 2-3; Fig 2-4; Ch 3 (3.1, 3.2)
2. FAA (2024c). ProFAA roughness software. ProFAA 3.1.0 (MER function), FAA Airport Technology R&D; release date unconfirmed. Original source.AC 150/5380-9 Ch 3 (2009 behaviour); TC-23/09 App E (2023 limits)
3. FAA (2023). Method to Identify and Quantify Multiple-Event Roughness, DOT/FAA/TC-23/09 (T. Gerardi, M. Gerardi, APR Consultants). Final Report, January 2023 (does not constitute FAA policy). Original source.Exec summary pp. ix-x; Sec 2 p. 2; Sec 2.1-2.3 pp. 2-3; Sec 3 p. 4; Sec 3.1 p. 9; Table 1 p. 7; App E pp. E-3/E-4, E-8/E-9
4. FAA (2024b). Airport Pavement Multiple-Event Roughness Detection and Evaluation, DOT/FAA/TC-24/14 (T. Gerardi, M. Gerardi). Final Report, August 2024 (does not constitute FAA policy). Original source.Exec summary; Sec 2.2, 2.3, 3.2, 3.3; 5.1.1-5.1.3; acronym list
5. Transport Canada (2016). AC 302-023, Measurement and Evaluation of Runway Roughness. Issue 02, effective 16 Dec 2016 (current per TC page, checked 3 Nov 2026). Original source.4.3(3); 5.1-5.3; 6.1 with Fig 1 and Table 1; 6.2 (IRI, RMSVA, RCI)

Use the manual edition and project requirements that apply to your work. Worked examples use synthetic values and are not site-specific design advice.